webadmin: edit inactive when VM is running

Edit button shouldn't be grayed out for
inactive disks when the VM is running.

Change-Id: I844c97b10dda22181f3f827970ae7aef837ea5c6
Bug-Url: https://bugzilla.redhat.com/963545
Signed-off-by: Daniel Erez <derez@redhat.com>