contrib: fix variable quoting
contrib: fix variable quoting

If we double quote the variables they will get interpreted between
single quote which will give us an error like 'git ls-remote --tags'
command not found.

Signed-off-by: Sébastien Han <62d754cc350e84d3b1c32ae79f976f5348e74a40@redhat.com>

ceph/ceph-docker,ceph/ceph-docker