virfiletest: Load mock on Linux only
virfiletest: Load mock on Linux only

The mock is built on Linux only. Therefore we should load it only
on Linux too. This fixes the FreeBSD build.

Signed-off-by: Michal Privoznik <83d82aaba2eed257f4814b0c239c260c4caaadf0@redhat.com>
Reviewed-by: Andrea Bolognani <3ada0bee826c753786fdbba72243dfba997094cf@redhat.com>

andreabolognani/libvirt,jardasgit/libvirt,eskultety/libvirt,fabianfreyer/libvirt,fabianfreyer/libvirt,crobinso/libvirt,jardasgit/libvirt,andreabolognani/libvirt,crobinso/libvirt,jfehlig/libvirt,nertpinx/libvirt,eskultety/libvirt,andreabolognani/libvirt,zippy2/libvirt,jardasgit/libvirt,libvirt/libvirt,jfehlig/libvirt,jfehlig/libvirt,olafhering/libvirt,olafhering/libvirt,fabianfreyer/libvirt,crobinso/libvirt,jfehlig/libvirt,zippy2/libvirt,zippy2/libvirt,zippy2/libvirt,nertpinx/libvirt,olafhering/libvirt,fabianfreyer/libvirt,nertpinx/libvirt,jardasgit/libvirt,eskultety/libvirt,crobinso/libvirt,nertpinx/libvirt,eskultety/libvirt,eskultety/libvirt,jardasgit/libvirt,libvirt/libvirt,olafhering/libvirt,libvirt/libvirt,andreabolognani/libvirt,nertpinx/libvirt,libvirt/libvirt,andreabolognani/libvirt,fabianfreyer/libvirt