travis: Run ArduSub test

Signed-off-by: Patrick José Pereira <patrickelectric@gmail.com>

Author: patrickelectric

.travis.yml

@@ -69,4 +69,4 @@ matrix:
       env: CI_BUILD_TARGET="sitltest-quadplane sitltest-plane"
     - if: type != cron
       compiler: "clang"
-      env: CI_BUILD_TARGET="sitltest-rover"
+      env: CI_BUILD_TARGET="sitltest-rover sitltest-sub""