gluster: move exportToSupervdsm at module level as makePublic

The scope of exportToSuperVdsm decorator is limited to cli.py.
It's moved to module level which enables the usage widely.
And the function name exportToSupervdsm changed into makePublic.

Change-Id: I5b8217899a637a10c7bc47a13e8afdddc1b0fefe
Signed-off-by: Timothy Asir <tjeyasin@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/13051
Reviewed-by: Dan Kenigsberg <danken@redhat.com>