Code cleanup: quota limit validation

In the quota limit validation, the conditional expressions are
difficult to understand because -1 which means an unlimited value is
compared directly.

By converting -1 to infinity, the validation can be implemented with
simple numeric comparisons. It makes code maintenance much easier.

Change-Id: I74650cba121734a14d31b76607adea004804c815
Merge "Code cleanup: quota limit validation"