mongotop_reports.js, mongotop_stress.js, and dump_server_ko_test.js need to check startParallelShell exit code

After https://github.com/mongodb/mongo/commit/0b879b315473bb2d0a296a782a1dc8cf7fac8e20, mongo shell now exits with 253 (-3) after a child task fails with unexpected error message.

In these tests, we can ignore the expected errors from the parallel shells.