Add ability to manually specify RPM package version number

While trying to package the Fluorine Managed Release Common Distribution as an RPM, I'm hitting an error because I had previously built the non-MR Fluorine release to the CentOS CBS. This is not a big problem, it's what the package version number after the minus is supposed to be used for. However, need to expose manually setting that version number, likely both in Int/Pack build logic and related Builder job logic.

cbs build nfv7-opendaylight-9-el7 opendaylight-9.0.0-1.el7.src.rpm
Uploading srpm: opendaylight-9.0.0-1.el7.src.rpm
[====================================] 100% 00:09:33 296.53 MiB 529.59 KiB/sec
Created task: 570813
Task info: https://cbs.centos.org/koji/taskinfo?taskID=570813
Watching tasks (this may be safely interrupted)...
570813 build (nfv7-opendaylight-9-el7, opendaylight-9.0.0-1.el7.src.rpm): free
570813 build (nfv7-opendaylight-9-el7, opendaylight-9.0.0-1.el7.src.rpm): free -> FAILED: GenericError: Build already exists (id=24119, state=COMPLETE): {'name': 'opendaylight', 'task_id': 570813, 'extra': None, 'pkg_id': 755, 'epoch': None, 'completion_time': None, 'state': 0, 'version': '9.0.0', 'source': None, 'volume_id': 0, 'owner': 60, 'release': '1.el7', 'start_time': 'NOW'}
0 free 0 open 0 done 1 failed

570813 build (nfv7-opendaylight-9-el7, opendaylight-9.0.0-1.el7.src.rpm) failed