webadmin: Fix "no quota in DC" message logic

The message which alerts the user about "no quotas in the DC" should
appear when moving between quota enforcement states:
  Disabled >> Enforced
  Audit >> Enforce
The message should not be presented when moving between
  Disabled >> Audit

Change-Id: If5774a42e890a93bc5d8779923cf857ae861f495
Bug-Url: https://bugzilla.redhat.com/974172
Signed-off-by: Ofri Masad <omasad@redhat.com>