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 "Stop ignoring 400 errors returned by ODL" into stable/icehouse