fix docker "dev" tag string (#611)

Author: jhoblitt

Makefile

@@ -3,7 +3,7 @@ GOPATH := $(shell go env GOPATH)
 # Sets the build version based on the output of the following command, if we are building for a tag, that's the build else it uses the current git branch as the build
 BUILD_VERSION:=$(shell git describe --exact-match --tags $(git log -n1 --pretty='%h') 2>/dev/null || git rev-parse --abbrev-ref HEAD 2>/dev/null)
 BUILD_TIME:=$(shell date 2>/dev/null)
-TAG ?= "minio/console:$(VERSION)-dev"
+TAG ?= "minio/console:$(BUILD_VERSION)-dev"
 
 default: console