ext4: avoid starting transaction on read-only fs in ext4_quota_off()

ext4: avoid starting transaction on read-only fs in ext4_quota_off()

When the filesystem gets first remounted read-only and then unmounted,
ext4_quota_off() will try to start a transaction (and fail) on read-only
filesystem to cleanup inode flags for legacy quota files. Just bail
before trying to start a transaction instead since that is going to
issue a warning.

Signed-off-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20230616165109.21695-6-jack@suse.cz
Signed-off-by: Theodore Ts'o <tytso@mit.edu>