Make it easier to debug swgger-gen flakes

Sometimes this check fails, but git status doesn't give us enough information
to debug the failure.

Signed-off-by: Daniel Nephin <dnephin@gmail.com>

hack/validate/swagger-gen

@@ -10,7 +10,7 @@ unset IFS
 if [ ${#files[@]} -gt 0 ]; then
 	${SCRIPTDIR}/../generate-swagger-api.sh 2> /dev/null
 	# Let see if the working directory is clean
-	diffs="$(git status --porcelain -- api/types/ 2>/dev/null)"
+	diffs="$(git diff -- api/types/)"
 	if [ "$diffs" ]; then
 		{
 			echo 'The result of hack/generate-swagger-api.sh differs'