Enable RPM build without ceph-test subpackage
A full build of ceph, including the ceph-test package, requires much more computational resources than building without ceph-test.
The ceph-test RPM is only needed for teuthology/ceph-qa-suite. In the course of development work, there are lots of scenarios when the ceph-test RPM is not needed.
Add a configure/%bcond knob to control whether the ceph-test RPM gets built.