If user hasn't supplied any tlsPort we default to setting it
to zero in our internal structure. However, when building command
line we test it against -1 which is obviously wrong.
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.