qemuTestDriverInit: Don't access live data

qemuTestDriverInit: Don't access live data

Some of our tests (e.g. qemuhotplugtest) call
virDomainSaveConfig(). Now the problem is, qemuTestDriverInit()
creates a fake qemu driver and fills it with some fake
configuration. At least so we hoped. The truth is, it calls
regular virQEMUDriverConfigNew() and then fix couple of paths.
Literally. Therefore our tests see regular stateDir and configDir
for the user that is running the tests. Directories, where live
domain XMLs are stored. Let's just hope our test suite hasn't
mangled any of them.

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>