Fixes code hint tests by controlling worker resets.

Previously, the web worker would be restarted at somewhat random
times during test runs (after a specific number of hints was requested).
This change forces the worker to start afresh with each test and switches
the worker so that it doesn't reset during any of the tests.
Re-enable some tests
Minor fixes in code hint test/debug code to address review comments.
Simplify setConfig in tern-worker by just using the entire new config object.
Merge pull request #5904 from adobe/dangoor/jshints-tests

Make JS code hint test runs more consistent