Adding class['swift'] as a dependency of the ring sync

If the directory /etc/swift doesn't exist when swift::ringsync
is run, then it silently fails to copy ringfiles.  Causing
service openstack-swift-* start
to fail. This dependency causes the sync to happen after
class['swift'] when we know /etc/swift exists.
https://bugzilla.redhat.com/show_bug.cgi?id=895116

Change-Id: I919ca3f943a47e5facd1d726f4314b8d59b27f35