jsonrpc: Bridge.py reducing logging level

There are two messages which are logged as warning but do not provide
any value in production.


Bug-Url: https://bugzilla.redhat.com/1151867
Change-Id: I69caf6ce30746ee3e8e843de8dcdddb793c55e2b
Signed-off-by: pkliczewski <piotr.kliczewski@gmail.com>
Reviewed-on: http://gerrit.ovirt.org/34097
Reviewed-by: Nir Soffer <nsoffer@redhat.com>
Reviewed-by: Dan Kenigsberg <danken@redhat.com>