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.

Conflicts:
        neutron/plugins/ml2/drivers/mechanism_odl.py

Closes-Bug: #1325184
Change-Id: I6b6153ea577bd685576690559b1c389490ee525d
(cherry picked from commit 903e2a8cd1dd9169048d1ad9dd8a566b2ae52395)
Stop ignoring 400 errors returned by ODL

This commit stops ignoring 400 (Bad Request) HTTP codes returned by ODL
in create and update operations. It also modifies sendjson() because it
doesn't ignore any HTTP error code now.

Closes-Bug: #1369239
Change-Id: Id0db2c0c1d8fddfbd16b3ce9476a2358e2ef1e49
(cherry picked from commit f1507d080d9840e4cb6c1d5cfe5a4b6c1443bd8f)
Merge "Add unit tests covering single operations to ODL" into stable/icehouse
Merge "Stop ignoring 400 errors returned by ODL" into stable/icehouse