tests: mark as passing with SANITIZE=leak

tests: mark as passing with SANITIZE=leak

The tests listed below, since previous commits, no longer trigger any
leak.

   + t1507-rev-parse-upstream.sh
   + t1508-at-combinations.sh
   + t1514-rev-parse-push.sh
   + t2027-checkout-track.sh
   + t3200-branch.sh
   + t3204-branch-name-interpretation.sh
   + t5404-tracking-branches.sh
   + t5517-push-mirror.sh
   + t5525-fetch-tagopt.sh
   + t6040-tracking-info.sh
   + t7508-status.sh

Let's mark them with "TEST_PASSES_SANITIZE_LEAK=true" to notice and fix
promptly any new leak that may be introduced and triggered by them in
the future.

Signed-off-by: Rubén Justo <rjusto@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>