webadmin: Fix QoS validator error tooltip

Fixed the validator of the QoS popup window (integer fields) to check a
specific int range.

Change-Id: I43448a1a6fed4551fbcfde8c50eb14c1ca3b3ac9
Bug-Url: https://bugzilla.redhat.com/987959
Signed-off-by: Ofri Masad <omasad@redhat.com>