gluster: use the any() builtin

use
  any()
instead of
  'True' in collection.

Tiny cleanup patch found while fixing the complains of pep8 1.5.5.

Change-Id: Ieb4bbf6e3ad64d4860f65dcba3fe88fab7472262
Signed-off-by: Francesco Romani <fromani@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/26765
Reviewed-by: Timothy Asir <tjeyasin@redhat.com>
Reviewed-by: Dan Kenigsberg <danken@redhat.com>