The existing log messages for this have several problems; there are
two lines of log when one will suffice, they duplicate the function
name in log message (when it's already included by VIR_DEBUG), they're
missing some useful bits, they get logged even when the call is a NOP.

This patch cleans up the problems with those existing logs, and also
adds a new VIR_INFO-level log down at the function that is actually
creating and sending the netlink message that logs *everything* going
into the netlink message (which turns out to be much more useful in
practice for me; I didn't want to eliminate the logs at the existing
location though, in case they are useful in some scenario I'm
unfamiliar with; anyway those logs are remaining at debug level, so it
shouldn't be a bother to anyone).