default permissions for $CHARM_DIR

[Mark Mims]

Please default charm directory permissions to 755 (or at least 711) instead of 700.

Charm directories are owned by root and default to 700. This causes problems for some charms that run as non-root users, but try to read files from the charm directory (nrpe).

related to https://bugs.launchpad.net/charms/+source/nrpe/+bug/1206018

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    ubuntu@ip-10-251-90-115:/var/lib/juju/agents$ ls -al unit-mysql-0/
    total 32
    drwxr-xr-x 4 root root 4096 Aug 12 18:05 .
    drwxr-xr-x 5 root root 4096 Aug 12 18:04 ..
    -rw------- 1 root root 13089 Aug 12 18:02 agent.conf
    drwx------ 7 root root 4096 Aug 12 18:05 charm
    drwxr-xr-x 5 root root 4096 Aug 12 18:05 state
    ubuntu@ip-10-251-90-115:/var/lib/juju/agents$ ls -al unit-nrpe-0/
    total 32
    drwxr-xr-x 4 root root 4096 Aug 12 18:05 .
    drwxr-xr-x 5 root root 4096 Aug 12 18:04 ..
    -rw------- 1 root root 13087 Aug 12 18:04 agent.conf
    drwx------ 6 root root 4096 Aug 12 18:05 charm
    drwxr-xr-x 5 root root 4096 Aug 12 18:05 state