Put correct gerrit ssh pubkey on git.o.o

The pubkey being used previous was the server pubkey, not the
gerrit2 user pubkey. The gerrit2 user pubkey is now in hiera
and switched git.openstack.org to use that for the
authorized_keys file.

Change-Id: I6665ef119071b8b68e4cb6bb7f7e8d79ad04fcbc