gluster: Improved audit log messages

The older messages logged by GlusterManager indicated that some action
was performed "from gluster cli". While this is true for most cases, it
can some times be misleading if some change is done implicitly by
glusterfs. Hence changing the messages to make them more generic.
Also added the cluster name to the messages.

e.g.

"Gluster Volume <volname> was created from gluster CLI.
Now added to engine DB as well."

changed to

"Detected new volume <volname> on cluster <clustername>,
and added it to engine DB"

Also removed the wrapper methods for audit logging, to make use of the
newly introduced GlusterAuditLogUtil.

Change-Id: I50396fb952001a65fa63e62e94b1fb8dc79b0858
Signed-off-by: Shireesh Anjal <sanjal@redhat.com>