Replace ConcurrentHashMap with HashMap in PipelineStateMap

There is a class PipelineStateMap with 2 fields:

1. ConcurrentHashMap<PipelineID, Pipeline> pipelineMap
2. ConcurrentHashMap<PipelineID, NavigableSet<ContainerID>> pipeline2container

Both read and write in PipelineStateMap are protected by lock in PipelineStateManagerImpl .

We can safely replace ConcurrentHashMap with pure HashMap