Fix test_suites.sh to fail if the chip-tool command fails.

If chip-tool crashed, the script was not treating this as a failure,
because the default exit code of a pipeline is that of the last
command in the pipeline and we are piping through tee.

scripts/tests/test_suites.sh

@@ -16,8 +16,13 @@
 # limitations under the License.
 #
 
+# Fail if one of our sub-commands fails.
 set -e
 
+# Fail if anything in a pipeline fails, not just the last command (which for
+# us tends to be 'tee').
+set -o pipefail
+
 declare -i iterations=2
 declare -i delay=0
 declare -i node_id=0x12344321