21779 - Errno::ESRCH: No such process from M::Shell

In the past when calling #runcommand an Errno::ESRCH exception would be
raised when the systemu process terminated correctly. This was the
expected behavior but caused the logs to be spammed with the message.

This commit changes #runcommand to quietly catch the Errno::ESRCH
exception.
21779 - Errno::ESRCH: No such process from M::Shell

update changelog