fernet_rotate_and_sync.py should use a mutex

[Felipe Reyes]

The cronjob fernet_rotate_and_sync.py should attempt to acquire a lock (file based) to prevent from having multiple instances running when the completion of the script is taking too long, in this case juju was running other hooks and it was not allowing leader-settings-changed hook to run.

root 118001 0.0 0.0 2888 988 ? Ss 17:34 0:00 /bin/sh -c /usr/bin/juju-run keystone/1 /var/lib/juju/agents/unit-keystone-1/charm/scripts/fernet_rotate_and_sync.py >> /var/log/keystone/keystone-fernet-rotate-sync.log 2>&1
root 118002 0.0 4.0 853896 81620 ? Sl 17:34 0:00 /usr/bin/juju-run keystone/1 /var/lib/juju/agents/unit-keystone-1/charm/scripts/fernet_rotate_and_sync.py
root 118740 0.0 0.0 2888 1064 ? Ss 17:35 0:00 /bin/sh -c /usr/bin/juju-run keystone/1 /var/lib/juju/agents/unit-keystone-1/charm/scripts/fernet_rotate_and_sync.py >> /var/log/keystone/keystone-fernet-rotate-sync.log 2>&1
root 118741 0.0 4.0 853896 81952 ? Sl 17:35 0:00 /usr/bin/juju-run keystone/1 /var/lib/juju/agents/unit-keystone-1/charm/scripts/fernet_rotate_and_sync.py
root 118764 0.0 0.0 2888 1004 ? Ss 17:36 0:00 /bin/sh -c /usr/bin/juju-run keystone/1 /var/lib/juju/agents/unit-keystone-1/charm/scripts/fernet_rotate_and_sync.py >> /var/log/keystone/keystone-fernet-rotate-sync.log 2>&1
root 118765 0.0 4.0 853896 82792 ? Sl 17:36 0:00 /usr/bin/juju-run keystone/1 /var/lib/juju/agents/unit-keystone-1/charm/scripts/fernet_rotate_and_sync.py
root 118788 0.0 0.0 2888 1040 ? Ss 17:37 0:00 /bin/sh -c /usr/bin/juju-run keystone/1 /var/lib/juju/agents/unit-keystone-1/charm/scripts/fernet_rotate_and_sync.py >> /var/log/keystone/keystone-fernet-rotate-sync.log 2>&1
root 118789 0.0 4.0 854152 82464 ? Sl 17:37 0:00 /usr/bin/juju-run keystone/1 /var/lib/juju/agents/unit-keystone-1/charm/scripts/fernet_rotate_and_sync.py
root 118813 0.0 0.0 2888 1000 ? Ss 17:38 0:00 /bin/sh -c /usr/bin/juju-run keystone/1 /var/lib/juju/agents/unit-keystone-1/charm/scripts/fernet_rotate_and_sync.py >> /var/log/keystone/keystone-fernet-rotate-sync.log 2>&1
root 118814 0.0 4.0 853896 81652 ? Sl 17:38 0:00 /usr/bin/juju-run keystone/1 /var/lib/juju/agents/unit-keystone-1/charm/scripts/fernet_rotate_and_sync.py
root 118837 0.0 0.0 2888 956 ? Ss 17:39 0:00 /bin/sh -c /usr/bin/juju-run keystone/1 /var/lib/juju/agents/unit-keystone-1/charm/scripts/fernet_rotate_and_sync.py >> /var/log/keystone/keystone-fernet-rotate-sync.log 2>&1
root 118838 0.0 4.0 853896 82448 ? Sl 17:39 0:00 /usr/bin/juju-run keystone/1 /var/lib/juju/agents/unit-keystone-1/charm/scripts/fernet_rotate_and_sync.py
root 118862 0.0 0.0 2888 948 ? Ss 17:40 0:00 /bin/sh -c /usr/bin/juju-run keystone/1 /var/lib/juju/agents/unit-keystone-1/charm/scripts/fernet_rotate_and_sync.py >> /var/log/keystone/keystone-fernet-rotate-sync.log 2>&1
root 118863 0.0 4.0 853896 82444 ? Sl 17:40 0:00 /usr/bin/juju-run keystone/1 /var/lib/juju/agents/unit-keystone-1/charm/scripts/fernet_rotate_and_sync.py
root 118886 0.0 0.0 2888 952 ? Ss 17:41 0:00 /bin/sh -c /usr/bin/juju-run keystone/1 /var/lib/juju/agents/unit-keystone-1/charm/scripts/fernet_rotate_and_sync.py >> /var/log/keystone/keystone-fernet-rotate-sync.log 2>&1
root 118887 0.0 4.0 853896 81668 ? Sl 17:41 0:00 /usr/bin/juju-run keystone/1 /var/lib/juju/agents/unit-keystone-1/charm/scripts/fernet_rotate_and_sync.py
root 118910 0.0 0.0 2888 984 ? Ss 17:42 0:00 /bin/sh -c /usr/bin/juju-run keystone/1 /var/lib/juju/agents/unit-keystone-1/charm/scripts/fernet_rotate_and_sync.py >> /var/log/keystone/keystone-fernet-rotate-sync.log 2>&1
root 118911 0.0 4.0 853896 82300 ? Sl 17:42 0:00 /usr/bin/juju-run keystone/1 /var/lib/juju/agents/unit-keystone-1/charm/scripts/fernet_rotate_and_sync.py
root 118934 0.0 0.0 2888 1036 ? Ss 17:43 0:00 /bin/sh -c /usr/bin/juju-run keystone/1 /var/lib/juju/agents/unit-keystone-1/charm/scripts/fernet_rotate_and_sync.py >> /var/log/keystone/keystone-fernet-rotate-sync.log 2>&1
root 118935 0.0 4.0 853896 82016 ? Sl 17:43 0:00 /usr/bin/juju-run keystone/1 /var/lib/juju/agents/unit-keystone-1/charm/scripts/fernet_rotate_and_sync.py
root 118958 0.0 0.0 2888 984 ? Ss 17:44 0:00 /bin/sh -c /usr/bin/juju-run keystone/1 /var/lib/juju/agents/unit-keystone-1/charm/scripts/fernet_rotate_and_sync.py >> /var/log/keystone/keystone-fernet-rotate-sync.log 2>&1
root 118959 0.0 4.0 853896 82268 ? Sl 17:44 0:00 /usr/bin/juju-run keystone/1 /var/lib/juju/agents/unit-keystone-1/charm/scripts/fernet_rotate_and_sync.py
root 118984 0.0 0.0 2888 988 ? Ss 17:45 0:00 /bin/sh -c /usr/bin/juju-run keystone/1 /var/lib/juju/agents/unit-keystone-1/charm/scripts/fernet_rotate_and_sync.py >> /var/log/keystone/keystone-fernet-rotate-sync.log 2>&1
root 118985 0.0 4.0 853896 82860 ? Sl 17:45 0:00 /usr/bin/juju-run keystone/1 /var/lib/juju/agents/unit-keystone-1/charm/scripts/fernet_rotate_and_sync.py
root 119008 0.0 0.0 2888 984 ? Ss 17:46 0:00 /bin/sh -c /usr/bin/juju-run keystone/1 /var/lib/juju/agents/unit-keystone-1/charm/scripts/fernet_rotate_and_sync.py >> /var/log/keystone/keystone-fernet-rotate-sync.log 2>&1
root 119009 0.0 4.0 853896 82096 ? Sl 17:46 0:00 /usr/bin/juju-run keystone/1 /var/lib/juju/agents/unit-keystone-1/charm/scripts/fernet_rotate_and_sync.py
root 119032 0.0 0.0 2888 964 ? Ss 17:47 0:00 /bin/sh -c /usr/bin/juju-run keystone/1 /var/lib/juju/agents/unit-keystone-1/charm/scripts/fernet_rotate_and_sync.py >> /var/log/keystone/keystone-fernet-rotate-sync.log 2>&1
root 119033 0.0 4.0 853896 82056 ? Sl 17:47 0:00 /usr/bin/juju-run keystone/1 /var/lib/juju/agents/unit-keystone-1/charm/scripts/fernet_rotate_and_sync.py
root 119057 0.0 0.0 2888 1004 ? Ss 17:48 0:00 /bin/sh -c /usr/bin/juju-run keystone/1 /var/lib/juju/agents/unit-keystone-1/charm/scripts/fernet_rotate_and_sync.py >> /var/log/keystone/keystone-fernet-rotate-sync.log 2>&1
root 119058 0.1 4.0 853896 81240 ? Sl 17:48 0:00 /usr/bin/juju-run keystone/1 /var/lib/juju/agents/unit-keystone-1/charm/scripts/fernet_rotate_and_sync.py
root 119081 0.0 0.0 2888 964 ? Ss 17:49 0:00 /bin/sh -c /usr/bin/juju-run keystone/1 /var/lib/juju/agents/unit-keystone-1/charm/scripts/fernet_rotate_and_sync.py >> /var/log/keystone/keystone-fernet-rotate-sync.log 2>&1
root 119082 0.2 4.0 853896 81152 ? Sl 17:49 0:00 /usr/bin/juju-run keystone/1 /var/lib/juju/agents/unit-keystone-1/charm/scripts/fernet_rotate_and_sync.py