Fix: Race condition on process kill: sometimes FIFO are still open

[penguinolog]

Log critical if readers are still running.
Allow exception on stream close (do not handle) to protect from leak.
Primary use SIGTERM for graceful shutdown, then retry with SIGKILL

[coveralls]

Pull Request Test Coverage Report for Build 318

• 8 of 11 (72.73%) changed or added relevant lines in 2 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-0.3%) to 99.303%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
exec_helpers/subprocess_runner.py	7	10	70.0%

Totals
Change from base Build 309:	-0.3%
Covered Lines:	998
Relevant Lines:	1005

---

💛 - Coveralls