xfs_admin: pick up log arguments correctly

xfs_admin: pick up log arguments correctly

In commit ab9d8d69, we added support to xfs_admin to pass an external
log to xfs_db and xfs_repair.  Unfortunately, we didn't do this
correctly -- by appending the log arguments to DB_OPTS, we now guarantee
an invocation of xfs_db when we don't have any work for it to do.

Brian Foster noticed that this results in xfs/764 hanging fstests
because xfs_db (when not compiled with libeditline) will wait for input
on stdin.  I didn't notice because my build includes libeditline and my
test runner script does silly things with pipes such that xfs_db would
exit immediately.

Reported-by: Brian Foster <bfoster@redhat.com>
Fixes: ab9d8d69 ("xfs_admin: support adding features to V5 filesystems")
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Eric Sandeen <sandeen@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Eric Sandeen <sandeen@sandeen.net>