qemu: Don't parse log output when starting up a domain

qemu: Don't parse log output when starting up a domain

Despite our great effort we still parsed qemu log output.
We wouldn't notice unless upcoming qemu 1.4 changed the
format of the logs slightly. Anyway, now we should gather
all interesting knobs like pty paths from monitor. Moreover,
since for historical reasons the first console can be just
an alias to the first serial port, we need to check this and
copy the pty path if that's the case to the first console.