The additional debug logging added with
https://git.opendaylight.org/gerrit/#/c/39796/ makes it too chatty with
heartbeats when nothing changed which will roll-over log files much more
quickly. Changed a debug to trace.
Change-Id: I4c204c6d0734d6ac8655380adcc2df09cb2890ae Signed-off-by: Tom Pantelis <tpanteli@brocade.com>