test: really run addon tests on `make test`

Fix a `s/addon/addons/` typo in the Makefile.

PR-URL: https://github.com/nodejs/node/pull/7542
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>

Makefile

@@ -118,7 +118,7 @@ test: all
 	$(MAKE) build-addons
 	$(MAKE) cctest
 	$(PYTHON) tools/test.py --mode=release -J \
-		addon doctool known_issues message pseudo-tty parallel sequential
+		addons doctool known_issues message pseudo-tty parallel sequential
 	$(MAKE) lint
 
 test-parallel: all