qemuxmlconftest: Move mock'd FDs further out

qemuxmlconftest: Move mock'd FDs further out

Upcoming patches will introduce use of real FDs for tests. Since the
test will go through many FDs they will collide with the fake ones
allocated randomly in qemuxml2argvmock.

Move them out for now until they are replaced and masked out from the
tests.

Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>