Add unit tests covering single operations to ODL

This commit adds the remaining test cases (create and update
operations) to fully cover sync_single_resource. It also defines the
filter_* methods as static or class methods and removes their duplicate
arguments.

Change-Id: I6b6153ea577bd685576690559b1c389490ee525d
Closes-Bug: #1325184
Merge "Add unit tests covering single operations to ODL"