test: update test-run

Run collectgarbage() between tests to ensure that there are no dangling
iterators and so on. Such objects can affect statistic counters that may
be important for a test.

Fixes #4287.

test-run @ 27aebd93

-Subproject commit 453d2bf3ed1df04757495171b18f8b0b6df1f448
+Subproject commit 27aebd93121769820c0983842b447642460a8aac