webadmin: adding labels column to Network->Hosts sub-tab

Adding a tag image to the device name column if the network is attacehd
via label.

Change-Id: I610703df29dcae7ace390e0ebb109475fb202263
Bug-Url: https://bugzilla.redhat.com/1063797
Signed-off-by: Alona Kaplan <alkaplan@redhat.com>