fix testsuite: make sure they use templates freshly built from the source

fix testsuite: make sure they use templates freshly built from the source

The initial t/trash repository for testing was created properly
but over time we gained many tests that create secondary test
repositories with init-db or clone and they were not careful
enough.

This fixes it.

Signed-off-by: Junio C Hamano <junkio@cox.net>