…8982)

- The pattern for parsing process IDs was too relaxed and would
match everything between the first opening and the last closing
square bracket in a message. If the message included multiple
closing square brackets, the process ID would be set to not only
the process ID, but also whatever leads up to the last closing
square bracket.
- The pattern has now been locked down to only digits.
- Added test case.

(cherry picked from commit 8e9a276)