VOL-4977 - Failure in voltha-protos verification job.

Makefile
makefiles/consts.mk
makefiles/include.mk
virtualenv.mk
requirements.txt
--------------------
  o Added library makefiles from repo:onf-make to handle virtualenv setup/removal.
  o go-clean - augment clean rule, current behavior leaves directory unbuildable.

makefiles/docker/include.mk
---------------------------
  o Replace inlined copies of docker cli arguments with macros: is-stdin, docker-run, etc.
  o Moved docker command wrappers: PROTOC, etc into docker/include.mk

makefiles/help/*.mk
-------------------
  o Update and align makefile target help text.

Change-Id: Ifcf72e8081efc6e0d828ee4b1b96c66a219a39b9
diff --git a/makefiles/lint/robot.mk b/makefiles/lint/robot.mk
index f33c4ba..dfbf034 100644
--- a/makefiles/lint/robot.mk
+++ b/makefiles/lint/robot.mk
@@ -38,6 +38,6 @@
 	    ; rflint $(LINT_ARGS) $(ROBOT_FILES)
 
 help::
-	@echo "  lint-robot           Syntax check robot sources using rflint"
+	@echo "  lint-robot                   Syntax check robot sources using rflint"
 
 # [EOF]