Merge branch 'jk/test-chainlint-softer'

Merge branch 'jk/test-chainlint-softer'

The "chainlint" feature in the test framework is a handy way to
catch common mistakes in writing new tests, but tends to get
expensive.  An knob to selectively disable it has been introduced
to help running tests that the developer has not modified.

* jk/test-chainlint-softer:
  t: avoid sed-based chain-linting in some expensive cases