The bin/tests/system/start.pl script truncates the named.run file for a
given named instance unless it is invoked with the --restart
command-line option. Ever since Python-based tests were introduced,
bin/tests/system/run.sh may start named instances used by a given system
test multiple times within a single run, causing the
bin/tests/system/start.pl script to truncate some of the log files
written during the test. This makes troubleshooting certain test
failures hard or even impossible.
Fix by calling bin/tests/system/start.pl with the --restart command-line
option for every start_servers() invocation except the first one.