This option accepts 3 values:
-keep, to keep current client connected (Spice+VNC)
-disconnect, to disconnect client (Spice)
-fail, to fail setting password if there is a client connected (Spice)
Alas, /usr/bin/kvm is also not directly supported by testutilsqemu.c.
In fact, _any_ test that uses <cpu match=...> has to use our faked
qemu.sh in order to properly answer the 'qemu -cpu ?' probe done
during qemu command line building.
* tests/qemuxml2argvdata/*graphics-spice-timeout*: Switch emulator, again.