xfs/019: extend protofile test

xfs/019: extend protofile test

This test creates an xfs filesystem and verifies that the filesystem
matches what is specified by the protofile.

This patch extends the current test to check that a protofile can
specify setgid mode on directories. Also, check that the created
symlink isn’t broken.

Signed-off-by: Catherine Hoang <catherine.hoang@oracle.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.org>
Signed-off-by: Eryu Guan <guaneryu@gmail.com>