started refactoring of node collection db calls
fixed tests. need to refactor network db calls
fix for flake8
tests for node collection handler
remove debug comments
eagerloading for node collection handler.
GET api/nodes takes about 2 sec
fix tests
fix flake8
revert flake8 back, diff versions of flake
Merge pull request #1581 from Mirantis/fix/node_collection_perfomance

refactoring of node collection db calls