qemu: blockjob: Track current state of blockjob

qemu: blockjob: Track current state of blockjob

Add a field tracking the current state of job so that it can be queried
later. Until now the job state e.g. that the job is _READY for
finalizing was tracked only for mirror jobs. Add tracking of state for
all jobs.

Similarly to 'qemuBlockJobType' this maps the existing states of the
blockjob from virConnectDomainEventBlockJobStatus to
'qemuBlockJobState' so that we can track some internal states as well.

Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>