xfs: test xfs_growfs with too-small size expansion

xfs: test xfs_growfs with too-small size expansion

This's a regression test of 84712492e6da ("xfs: short circuit
xfs_growfs_data_private() if delta is zero").

If try to do growfs with "too-small" size expansion, might lead to a
delta of "0" in xfs_growfs_data_private(), then end up in the shrink
case and emit the EXPERIMENTAL warning even if we're not changing
anything at all.

Signed-off-by: Zorro Lang <zlang@redhat.com>
Reviewed-by: David Disseldorp <ddiss@suse.de>
Signed-off-by: Zorro Lang <zlang@kernel.org>