webadmin: Implement sorting for network roles column

Implemented logic to compare between network roles in the
Network/Clusters subtab.

Change-Id: Icd9fa5bfee38e9b46f94708f5b4d88240261b404
Bug-Url: https://bugzilla.redhat.com/1120054
Signed-off-by: Lior Vernia <lvernia@redhat.com>