Webadmin - Incorrect error message when selecting multiple Hosts from different DCs and openging a report

when selecting multiple Hosts from different
DCs and openging a report Via webadmin. An incorrect
error message is displayed

"Please select reports from the same data center"

The message should be rephrased

"Please select Hosts from the same data center"

Change-Id: If65b6790383840bbebb08a147902dcc3b9f18d04
Bug-Url: https://bugzilla.redhat.com/885983
Signed-off-by: Ravi Nori <rnori@redhat.com>