VOL-3978 - change the version of build tools

- fixed two minor errors in code that go 1.16 vet caught

Change-Id: Ibc5d7e966cb89bdb557a640fac70e2101a7b27b6
diff --git a/Makefile b/Makefile
index 7ffcaa0..1be409a 100644
--- a/Makefile
+++ b/Makefile
@@ -21,7 +21,7 @@
 VERSION                    ?= $(shell cat ./VERSION)
 
 # tool containers
-VOLTHA_TOOLS_VERSION ?= 2.3.1
+VOLTHA_TOOLS_VERSION ?= 2.4.0
 
 GO                = docker run --rm --user $$(id -u):$$(id -g) -v ${CURDIR}:/app $(shell test -t 0 && echo "-it") -v gocache:/.cache -v gocache-${VOLTHA_TOOLS_VERSION}:/go/pkg voltha/voltha-ci-tools:${VOLTHA_TOOLS_VERSION}-golang go
 GO_JUNIT_REPORT   = docker run --rm --user $$(id -u):$$(id -g) -v ${CURDIR}:/app -i voltha/voltha-ci-tools:${VOLTHA_TOOLS_VERSION}-go-junit-report go-junit-report