engine, webadmin: Webadmin read reports.xml from remote reports app

in 3.5 report can be installed in separate server.
Webadmin needs to be able to read reports.xml from
that location via http.

Change-Id: I76db7ab889f21de083bb3c8276e8abb77b68fdb3
Bug-Url: https://bugzilla.redhat.com/1116851
Signed-off-by: Ravi Nori <rnori@redhat.com>