Log OvsdbAppException as warnings
Log OvsdbAppException as warnings

To reduce amount of unnecessary tracebacks,
since most of the time we ignore all exceptions from OVSDB
and only log them, lower log level of OvsdbAppException
in ovs_lib from exception to warning, when check_error=False.

Change-Id: If5f95ccf9d90d77729dcaac543ad629e28a1f51d

openstack/neutron,mahak/neutron,openstack/neutron,mahak/neutron,mahak/neutron,openstack/neutron