Fix race conditions between config-manager and persister.

Config-manager commits a blank transaction each time new ModuleFactory is discovered. At the same time
persister might try to push configuration. Add retries to both routines to overcome optimistic lock failure.

Change-Id: Ia45505d285b2eb6cc7fa949289a3fbeb4c62f9e7
Signed-off-by: Tomas Olvecky <tolvecky@cisco.com>