Update edx-lint to the version that checks if tearDown uses super.

Convert a number of tearDown methods into addCleanup.

Remove some unneeded tearDown methods: no need to call patch.stopall if
none of them were started with patch.start.

Previously, authentication was done using a URL parameter, which would
appear in various logs. Now, authentication is done more appropriately
with an HTTP header. Note that this requires cs_comments_service commit
cf39aabdd160176ebf206ca19d3ee030161a0b47 or later.