test-lib: do not remove trash_directory if called with --debug
test-lib: do not remove trash_directory if called with --debug

Sometimes you want to keep the trash directory, even if all tests
passed.  For example, when extending tests, it comes it quite handy.

Signed-off-by: Johannes Schindelin <53fb8db7833fca1e1746dd8592f61048d350f64c@gmx.de>
Signed-off-by: Junio C Hamano <a6723cc3f76163bf7adb636a73ac3b0ceb3e6b9b@pobox.com>

destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git