According to the documentation:
The quota can have three types of values : (1) 0 or more will set
the quota to that value, (2)
the quota will not be changed, and (3)
implies the quota will be reset. Any other value is a runtime error.
sanity check in FsDirectory.unprotectedSetQuota should use
Since HdfsConstants.QUOTA_RESET is defined to be -1, there is not any problem for this code, but it is better to do it right.