build(travis): gracefully shut down the sauce connect tunnel after the tests are done running

This is to prevent tunnel leaks which cause us to run out of allocated tunnels.

Closes #4329

scripts/ci/after-script.sh

@@ -2,9 +2,13 @@
 set -e -o pipefail
 
 echo '*******************'
-echo '** AFTER_SUCCESS **'
+echo '** AFTER_SCRIPT **'
 echo '*******************'
 
+if [ "$MODE" = "saucelabs" ]; then
+  ./scripts/sauce/sauce_connect_teardown.sh
+fi
+
 
 echo '---------------------'
 echo '-- WAIT FOR OTHERS --'

scripts/sauce/sauce_connect_teardown.sh

@@ -0,0 +1,7 @@
+#!/bin/bash
+
+set -e -o pipefail
+
+
+echo "Shutting down Sauce Connect tunnel"
+killall sc