qemu: Fix virDoes*Exist usage
qemu: Fix virDoes*Exist usage

The virGet*ID() functions should be called only if the user exists not when it
doesn't.

Signed-off-by: Martin Kletzander <e82f23e74d43760279ebcc505dac4ae70d5627d0@redhat.com>

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