vircapstest: Avoid (im)possible strcmp call with NULL argument
vircapstest: Avoid (im)possible strcmp call with NULL argument

Some compilers may get confused and decide we are calling strcmp with
NULL argument from test_virCapsDomainDataLookupLXC. Although this does
not really happen since the call is guarded with
(data->machinetype != expect_machinetype), using STRNEQ_NULLABLE is
easier to understand, less fragile, and doing so makes sure strcmp is
never called with NULL argument.

Signed-off-by: Jiri Denemark <62bdf77dc47919a4d59a91822129d14633cfca81@redhat.com>

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