qemu: Fix incorrect jump labels in error paths
    
    Fix incorrect jump labels in error paths as the stop jump is only
    needed if the driver has already changed the state. For example
    'virAtomicIntInc(&driver->nactive)' will be 'reverted' in the
    qemuProcessStop call.
    
    Signed-off-by: Marc Hartmayer <mhartmay@linux.vnet.ibm.com>
    Reviewed-by: Boris Fiuczynski <fiuczy@linux.vnet.ibm.com>
    Signed-off-by: Michal Privoznik <mprivozn@redhat.com>