Fix failing IT tests

- Binding Test Helper did not spefied object-cache as dependency
  and it was already part of distribution
- API Doc plugin was using invalid YANG files for positive
  test scenario.

Change-Id: I06c174408df6073d887f5c307cf1b70c34c442b1
Signed-off-by: Maros Marsalek <mmarsale@cisco.com>
Merge "Fix failing IT tests"