install packages for tests

Running `go test -i` installs the requirements for a package's tests.
This way when running the tests in batches of 4, we can cut the runtime
in half be only compiling the dependencies once.

Makefile

@@ -39,6 +39,7 @@ plugin-dev: generate
 
 # test runs the unit tests
 test:# fmtcheck errcheck generate
+	go test -i $(TEST) || exit 1
 	echo $(TEST) | \
 		xargs -t -n4 go test $(TESTARGS) -timeout=30s -parallel=4