[gluster] tidy up add_copy_spec() usage

The gluster plugin has a pile of fragmented add_copy_spec() calls.
Consolidate them into as few add_copy_specs() calls as possible
and remove the cargo-cult positioning of logs at the end.

Signed-off-by: Bryn M. Reeves <bmr@redhat.com>
[gluster] add redhat-storage-release

Fixes #329.

Signed-off-by: Bryn M. Reeves <bmr@redhat.com>