Set -x in the integration test (#522)

* Set -x in the integration test

The integration test has been flaking from time to time on Travis with
no obvious failures, indicating this is happening unexpectedly outside a
`fail` call.  `set -x` will help us diagnose when it happens again.

* Only show logs on test failure

* Correctly continue if test.sh fails

* Only cleanup the logfile on success.  The logfile should stick around on
failure for easier sharing of test results.  It will eventually get
cleaned up whenever the tmp directory gets cleaned.

src/shadowbox/integration_test/run_action.sh

@@ -16,5 +16,20 @@
 
 do_action shadowbox/docker/build
 
+LOGFILE=$(mktemp)
+echo "Running Shadowbox integration test.  Logs at $LOGFILE"
+
 cd src/shadowbox/integration_test
-./test.sh
+
+result=0
+
+if ./test.sh > $LOGFILE 2>&1 ; then
+  echo "Test Passed!"
+  rm $LOGFILE
+else
+  result=$?
+  echo "Test Failed!  Logs:"
+  cat $LOGFILE   
+fi
+
+exit $result

src/shadowbox/integration_test/test.sh

@@ -30,6 +30,8 @@
 #
 # Each node runs on a different Docker container.
 
+set -x
+
 export DOCKER_CONTENT_TRUST=${DOCKER_CONTENT_TRUST:-1}
 
 readonly OUTPUT_DIR=$(mktemp -d)