build(travis): block travis while we are shutting down the tunnel

This is to prevent Travis from prematurely shut down the VM while we are still waiting for the sauce connect client
to tear down the tunnel.

Closes #4335

scripts/sauce/sauce_connect_teardown.sh

@@ -4,4 +4,13 @@ set -e -o pipefail
 
 
 echo "Shutting down Sauce Connect tunnel"
+
 killall sc
+
+while [[ -n `ps -ef | grep "bin/sc" | grep -v "grep"` ]]; do
+  printf "."
+  sleep .5
+done
+
+echo ""
+echo "Sauce Connect tunnel has been shut down"