Address map access data race in matching engine

[taylanisikdemir]

What changed?
A PR check test was failing due to unprotected access to taskLists by multiple goroutines. Handling it by deferring unlock which is generally safer way to use mutex.

Misc changes:

• Get rid of inconsistent/unnecessary usage of multilines. Hurts vertical readability speed.

Why?
Avoid data race. This will also decrease flakiness of the tests.

[3vilhamster]

Good catch. I wonder how we did not see it in prod.

[taylanisikdemir]

Good catch. I wonder how we did not see it in prod.

This happens during tasklist stop flow so not likely to hit or detect in prod.