* filer: allow clearing a bucket read-only flag stuck after quota removal
Once s3.bucket.quota.enforce marks a bucket read-only, removing or
disabling the quota orphans the flag: enforcement skips buckets with a
non-positive quota, and fs.configure merges booleans with OR so
-readOnly=false could never turn it off. The only way out was deleting
the whole path rule.
- s3.bucket.quota -op=remove/disable and the admin server quota update
now lift the read-only flag on the bucket's path rule
- fs.configure now honors explicitly passed false boolean flags
(-readOnly, -fsync, -worm) instead of OR-merging them away
* filer: ClearBucketReadOnly reports unchanged when the save fails