Run system tests with set -e

Ensure all shell system tests are executed with the errexit option set.
This prevents unchecked return codes from commands in the test from
interfering with the tests, since any failures need to be handled
explicitly.

bin/tests/system/limits/tests.sh

@@ -11,6 +11,8 @@
 # See the COPYRIGHT file distributed with this work for additional
 # information regarding copyright ownership.
 
+set -e
+
 . ../conf.sh
 
 DIGOPTS="-p ${PORT}"