xfstests: mount all filesystem typess with selinux context when needed

xfstests: mount all filesystem typess with selinux context when needed

For some reason, non-xfs filesystems weren't getting mounted with
the selinux context; perhaps because none of the xattr tests used
to work on anything but xfs?

Anyway, 062 fails for extN unless we mount with the fs-wide
context.

So export SELINUX_MOUNT_OPTIONS for all filesystems.

Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>