If msi_init fails, the thread has already been created and the
mutex/condvar are not destroyed. Initialize everything only
after the point where pci_edu_realize cannot fail.
Reported-by: Markus Armbruster <armbru@redhat.com>
Cc: Peter Xu <peterx@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>