Reap failure can show red herring error message

[coderanger]

If an exception is raised during run_command, we try to reap things, it will show a red herring error log that "Command exceeded allowed execution time" even though the timeout wasn't involved. We should differentiate the log message on the two places we use reap_errant_child.

In this case the exception was being raised by a faulty live_stream implementation, but there are others.