Merge branch 'dt/gc-ignore-old-gc-logs'

Attempt to allow us notice "fishy" situation where we fail to
remove the temporary directory used during the test.

* dt/gc-ignore-old-gc-logs:
test-lib: retire $remove_trash variable
test-lib.sh: do not barf under --debug at the end of the test
test-lib: abort when can't remove trash directory

diff --cc t/test-lib.sh
Simple merge