qemu_process: check for correct return value while starting domain

Function qemuProcessLaunch returns '-2' in case there was an error and
we need to cleanup labels.

Signed-off-by: Pavel Hrdina <phrdina@redhat.com>

src/qemu/qemu_process.c

@@ -5458,7 +5458,7 @@ qemuProcessStart(virConnectPtr conn,
 
     if ((rv = qemuProcessLaunch(conn, driver, vm, asyncJob, incoming,
                                 snapshot, vmop, flags)) < 0) {
-        if (rv == -1)
+        if (rv == -2)
             relabel = true;
         goto stop;
     }