restapi : Non admin user have access to /hosts url (#909692)

Non admin users should not be able to see hosts using /api/hosts

Change-Id: I496a9560d462156944c3aa23b61d2b6d587d1700
Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=909692
Signed-off-by: Ravi Nori <rnori@redhat.com>
Signed-off-by: Yair Zaslavsky <yzaslavs@redhat.com>