Introduce a common interface or base class among Pipeline and multi node pipeline classes

[sazzad16]

Concerned methods:

• sync()
• close()

[sazzad16]

Currently, Pipeline already extends Queable which is common with Transaction classes. Because we can't extend more than once, right now it is not possible to simply create PipelineBase class and extend from Pipeline. Now, perhaps, it is more important to share a common PipelineBase among Pipeline and multi node pipeline classes than to share Queable among Pipeline and Transaction classes.