Fix NPE when deserializing a null Map

DATAREDIS-138
Fix Jedis dbSize and flush ops executing synchronously while in pipeline or tx

DATAREDIS-141
Fix Lettuce exec to return null when pipelining

DATAREDIS-139
Fix Lettuce zCount/zInterStore ops executing synchronously while in pipeline

DATAREDIS-140
Fix RJC zRevRangeWithScores returns incorrect results

DATAREDIS-137
Fix RJC ping executing synchronously while in pipeline
Fix SRP zCount/zInterStore methods executing synchronously when pipelining

DATAREDIS-142