Description of problem:
button Save Network Configuration is always grayed out, (screenshot 1)

it does not matter whether network is added/edited/detached

it also does not matter if the change is done the "old" way or via Setup Host Networks dialog

Version-Release number of selected component (if applicable):
oVirt Enterprise Virtualization Engine Manager Version: 3.1.0_0001-11.el6ev 

How reproducible:
100%

Steps to Reproduce:
for DC/cluster 3.0

1. add network to cluster
2. Hosts -> your host -> Network Interface -> free NIC -> add/edit -> 
   a) pick your network -> make sure Save network configuration is unchecked -> click OK

optional:
3. select NIC from step 2 -> detach -> click OK
  
Actual results:
button Save Network Configuration is always grayed out

Expected results:
button Save Network Configuration is active when network setting is changed and unsaved

Additional info:
tested for DC/cluster 3.1 and for DC/cluster 3.0