Merge branch 'ps/test-set-e-clean'

Merge branch 'ps/test-set-e-clean'

The test suite harness and many individual test scripts have been
updated to work correctly when 'set -e' is in effect, which helps
detect misspelled test commands.

* ps/test-set-e-clean:
  t: detect errors outside of test cases
  t9902: fix use of `read` with `set -e`
  t6002: fix use of `expr` with `set -e`
  t1301: don't fail in case setfacl(1) doesn't exist or fails
  t0008: silence error in subshell when using `grep -v`
  t: prepare `test_when_finished ()`/`test_atexit()` for `set -e`
  t: prepare execution of potentially failing commands for `set -e`
  t: prepare conditional test execution for `set -e`
  t: prepare `git config --unset` calls for `set -e`
  t: prepare `stop_git_daemon ()` for `set -e`
  t: prepare `test_must_fail ()` for `set -e`
  t: prepare `test_match_signal ()` calls for `set -e`