webadmin: Change running vm column

Change the "running vm" column in main tab Host to "Virtual Machines"
(counting total number of VMs on the host)

Change-Id: I19d06e11a2db1dd70471999064dc0480f81c0e17
Bug-Url: https://bugzilla.redhat.com/890823
Signed-off-by: Ofri Masad <omasad@redhat.com>