[Newton] hostname instability after fresh deployment

[Michele Baldessari]

After a fresh (as of today) deployment of newton we noticed the following in the output of
"neutron agents-list" on the overcloud:
| c16840b4-2ab9-4858-9839-032b10817b30 | Open vSwitch agent | overcloud-controller-1 | | :-) | True | neutron-openvswitch-agent |
| caa02fbb-3663-4f33-982e-a83a33042876 | Open vSwitch agent | overcloud-novacompute-0.localdomain | | :-) | True | neutron-openvswitch-agent |

Now after rebooting controller-1 we observe that we have double-entries in neutron agent-list for each
controller (one with .localdomain and one without). For example if I reboot only controller-0 after
a fresh install, I observe:
[stack@undercloud ~]$ neutron agent-list|grep controller-0
| 01fb71be-5af4-4d92-8562-a9fa5baac012 | DHCP agent | overcloud-controller-0 | nova | xxx | True | neutron-dhcp-agent |
| 1024f871-97ee-479d-8eae-222e8b5e946a | Open vSwitch agent | overcloud-controller-0 | | xxx | True | neutron-openvswitch-agent |
| 202dfbd4-bd05-405b-8510-fdf41818078c | DHCP agent | overcloud-controller-0.localdomain | nova | :-) | True | neutron-dhcp-agent |
| 40644602-0734-432f-8b63-858f14c270e7 | Metadata agent | overcloud-controller-0.localdomain | | :-) | True | neutron-metadata-agent |
| 8dbb2545-e988-444c-bf4c-a1449a1257ac | L3 agent | overcloud-controller-0.localdomain | nova | :-) | True | neutron-l3-agent |
| 9cf789ec-0970-4377-83e5-0ec778488769 | Metadata agent | overcloud-controller-0 | | xxx | True | neutron-metadata-agent |
| a51f440d-7719-4358-a35e-e14e7e297d8a | Open vSwitch agent | overcloud-controller-0.localdomain | | :-) | True | neutron-openvswitch-agent |
| cc71f0a9-f63d-46f9-9130-33fc231e57d5 | L3 agent | overcloud-controller-0 | nova | xxx | True | neutron-l3-agent |

What might trigger this behaviour is the following fact. Right after the initial deployment, on the
controllers you get the following:
[root@overcloud-controller-0 ~]# hostname
overcloud-controller-0
[root@overcloud-controller-0 ~]# hostname -f
overcloud-controller-0.localdomain

[root@overcloud-controller-0 etc]# hostnamectl
   Static hostname: overcloud-controller-0.localdomain
Transient hostname: overcloud-controller-0
         Icon name: computer-vm
           Chassis: vm
        Machine ID: 027a07d166557094b759a31ef1ce5c65
           Boot ID: 3869128a64a24cb9bb4cf42e6bd3666a
    Virtualization: kvm
  Operating System: CentOS Linux 7 (Core)
       CPE OS Name: cpe:/o:centos:centos:7
            Kernel: Linux 3.10.0-327.22.2.el7.x86_64
      Architecture: x86-64
[root@overcloud-controller-0 etc]# uname -a
Linux overcloud-controller-0 3.10.0-327.22.2.el7.x86_64 #1 SMP Thu Jun 23 17:05:11 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux

But after a reboot you will see this:
[heat-admin@overcloud-controller-0 ~]$ hostname
overcloud-controller-0.localdomain
[heat-admin@overcloud-controller-0 ~]$ hostname -f
overcloud-controller-0.localdomain

[root@overcloud-controller-0 ~]# hostnamectl
   Static hostname: overcloud-controller-0.localdomain
         Icon name: computer-vm
           Chassis: vm
        Machine ID: 027a07d166557094b759a31ef1ce5c65
           Boot ID: eec03ae0d1584ae281112ed2fab482f7
    Virtualization: kvm
  Operating System: CentOS Linux 7 (Core)
       CPE OS Name: cpe:/o:centos:centos:7
            Kernel: Linux 3.10.0-327.22.2.el7.x86_64
      Architecture: x86-64

Notice the a) absence of a Transient hostname in hostnamectl and b) the fully qualified hostname on both hostname *and* hostname -f commands

[Michele Baldessari (michele)]

I think this has been fixed via:
https://review.openstack.org/304858