libvirt: log all flags parameters

libvirt: log all flags parameters

I was testing a virsh patch, and wanted to see if I had passed the
flags I thought.  But with LIBVIRT_DEBUG in the environment, I just
saw:

14:24:52.359: 15022: debug : virDomainSnapshotNum:15586 : dom=0xc9c180, (VM: name=rhel_6-64, uuid=48f8e8e7-e14f-0e14-02f0-ce71997bdcab),

including a trailing space.  This fixes the issues.

* src/libvirt.c: Log flag parameters, even if currently unused.
(VIR_DOMAIN_DEBUG_0): Drop trailing comma in log.
(VIR_DOMAIN_DEBUG_1): Split guts into...
(VIR_DOMAIN_DEBUG_2): ...new macro.