Inconsistence behavior between mapdb and cassandra

[yichen88]

• Do you want to request a feature or report a bug?

• What is the current behavior?
  For most getFoo(String nodeId) methods:
  in mapdb, it checks existence and throws exception if not exists
  but in cassandra, it only check nodeId uuid's formats. And return un empty collections if node not found.

• If the current behavior is a bug, please provide the steps to reproduce and if possible a minimal demo of the problem

• What is the expected behavior?

• What is the motivation / use case for changing the behavior?

• Please tell us about your environment:

  • PowSyBl Version: ...
  • OS Version: ...

• Other information (e.g. detailed explanation, stacktraces, related issues, suggestions how to fix, links for us to have context, eg. stackoverflow, spectrum, etc)

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