tune2fs: more respect for quota config option

tune2fs: more respect for quota config option

Commit 44a2cca3 disabled tune2fs -O quota when the build
didn't have --enable-quota at configure time, but that
wasn't quite enough.

We need to exclude the "-Q" option as well from tune2fs
when --enable-quota isn't specified at configure time.

Otherwise, tune2fs -Q can set the quota feature, but no other
utility will touch the filesystem due to the unknown flag,
if buitl w/o --enable-quota.

So put everything related to "-Q" under #ifdef CONFIG_QUOTA;
usage output (was missing before) and option parsing.

Addresses-Red-Hat-Bugzilla: #1010709
Reported-by: Bert DeKnuydt <Bert.Deknuydt@esat.kuleuven.be>
Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>