Summary:
Sometimes after unit tests run, some Yb Controller processes are left behind
```
/bin/bash /tmp/yb_test.tmp.23006.2616.30551.pid2297555/ybc-2/tmp/yb-controller-tmp/coprocess/snapshot
```

We can use the ybc tmp dir to weed out these processes and kill them during YB controller termination.
Jira: DB-13152

Test Plan: Ran tests in parallel locally and made sure no processes are left behind. Jenkins.

Reviewers: loginov

Reviewed By: loginov

Subscribers: ybase

Differential Revision: https://phorge.dev.yugabyte.com/D38670