webadmin: Disable Host/Interfaces subtab refresh pre-3.1

In pre-3.1 clusters, host networking is setup through the subtab, and
refreshing the subtab (for the statistics) makes that hard to do as it
resets the row selection.

Change-Id: Idb1d14be079936eac2fb302320eb7000e970bc32
Bug-Url: https://bugzilla.redhat.com/1027597
Signed-off-by: Lior Vernia <lvernia@redhat.com>