Merge pull request #2676 from hashicorp/f-go-1.7.4

Updates Consul to build with Go 1.7.4.

.travis.yml

@@ -1,7 +1,7 @@
 language: go
 
 go:
-  - 1.7.3
+  - 1.7.4
 
 branches:
   only:

scripts/consul-builder/Dockerfile

@@ -1,6 +1,6 @@
 FROM ubuntu:trusty
 
-ENV GOVERSION 1.7.3
+ENV GOVERSION 1.7.4
 
 RUN apt-get update -y && \
     apt-get install --no-install-recommends -y -q \