qemu: fix ethernet network type ip/route assign
    
    The call to virNetDevIPInfoAddToDev() that sets up tap device IP
    addresses and routes was somehow incorrectly placed in
    qemuInterfaceStopDevice() instead of qemuInterfaceStartDevice() in
    commit fe8567f6.  This fixes that error by moving the call to
    virNetDevIPInfoAddToDev() to qemuInterfaceStartDevice().
    
    Signed-off-by: Vasiliy Tolstov <v.tolstov@selfip.ru>