webadmin: Change move to quota enforcing mode message

The message presented when moving the DC into enforcing quota mode was
rephrased.

Change-Id: Ie24d00f6523d4600962820ff2b88ed4eaf60443f
Bug-Url: https://bugzilla.redhat.com/903684
Signed-off-by: Ofri Masad <omasad@redhat.com>