qemu: Finish device removal in the original thread

qemu: Finish device removal in the original thread

If QEMU supports DEVICE_DELETED event, we always call
qemuDomainRemoveDevice from the event handler. However, we will need to
push this call away from the main event loop and begin a job for it (see
the following commit), we need to make sure the device is fully removed
by the original thread (and within its existing job) in case the
DEVICE_DELETED event arrives before qemuDomainWaitForDeviceRemoval times
out.

Without this patch, device removals would be guaranteed to never finish
before the timeout because the could would be blocked by the original
job being still active.

Signed-off-by: Jiri Denemark <jdenemar@redhat.com>