BUG 2676 : Reduce default logging in Dummy Data Store

Reduce the default log level to error and added a diagnostic
log message to detect situations where an append entries does
not get sent in a reasonable amount of time (5 seconds)

Change-Id: I46b7b20688207318dcfec2b209519761ecf1d93d
Signed-off-by: Moiz Raja <moraja@cisco.com>