virt-qemu: Add the ability to test multiple qemu binaries at once

[lmr]

It's interesting for regression testing that we specify multiple qemu binaries, and to allow using multiple binaries inside the test. Some API to conveniently change the qemu binary used by the qemu vm class would also be a nice addition. Something like:

vm.change_binary('/path/to/new/bin')

That would stop the vm, update params and restart the vm with the new binary.

[imammedo]

I'd suggest to have ability to set it via params dictionary as well using the same key as in configs. That way users that know about this parameter wouldn't have to dig inside vm source to find-out if there is a function to change qemu binary. Generally allowing to change vm.params before VM is created would be a rather flexible way to modify qemu behaviour in a way test wants.

[lmr]

Ok, fair enough. I'll take this into consideration while working on a solution, thanks!