nfs: recognise IPv6 export in _require_scratch_nocheck()

nfs: recognise IPv6 export in _require_scratch_nocheck()

This commit

73dfa4a common: Fixes for testing NFS over IPv6

adds NFS over IPv6 support, and commit

76c5f3c common: re-enable tests that require scratch dev on NFS

enables NFS tests on scratch device.

Now do the same updates to _require_scratch_nocheck() to enable NFS over
IPv6 support on scratch device.

Signed-off-by: Eryu Guan <eguan@redhat.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>