webadmin: add isCancel to command in quota

In quota model and quota list model the Cancel command was not set
with the isCancel attribute resaulting in problems when trying to
use the ESC key to clsoe it.

Change-Id: Ifb28b8c52b958f4d7ee62009e0d5114bf5268f50
Bug-Url: https://bugzilla.redhat.com/915759
Signed-off-by: Noam Slomianko <nslomian@redhat.com>