don't print stack trace when the ha broker is unreachable

Change-Id: I02cfcd2a59ede40efaa0747a7dd3b9758ffb5270
Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=1150073
Signed-off-by: Jiri Moskovcak <jmoskovc@redhat.com>