[multistage] QueryRunnerTest tear down takes 10sec (default timeout)

this very likely indicates some type of resource leak when issuing purposefully malicious queries, which is some of the test cases in this class do

need investigate on whether this is a test setup issue or an actual resource leak in main/prod code.

Start with the multistage QueryRunnerTest teardown and its cases that issue purposefully malicious queries. Investigate whether the 10-second default-timeout wait comes from test setup or a resource leak in production code. Done means the cause is identified and the test teardown no longer incurs the unexplained delay.

Written by the indexing model from the issue text.