qemu: Resolve Coverity RESOURCE_LEAK

qemu: Resolve Coverity RESOURCE_LEAK

This seemed to be more of a false positive as for some reason Coverity
was missing the "ret < 0" goto error condition and somehow believing that
event could be overwritten.  At first I thought it was just the ret != 0
condition difference, but it wasn't.

In any case, make use of the recent change to qemuDomainEventQueue to
check event == NULL and just pass it as a parameter directly in the
error path. That avoids the error.

Signed-off-by: John Ferlan <jferlan@redhat.com>