travis: Add a job checking coredhcp-generator/coredhcp sync

This ensures modifications in cmds/coredhcp-generator and cmds/coredhcp
are in sync

Signed-off-by: Anatole Denis <anatole@unverle.fr>

.travis.yml

@@ -43,3 +43,8 @@ script: |
 after_success:
   - bash <(curl -s https://codecov.io/bash)
 
+
+jobs:
+  include:
+    - name: Generator/main entrypoint drift
+      script: ./.travis/check-generator-main.sh

.travis/check-generator-main.sh

@@ -0,0 +1,12 @@
+#!/usr/bin/env bash
+
+set -ex
+
+# Build the generator version
+pushd cmds/coredhcp-generator
+go build
+generated=$(./coredhcp-generator -from core-plugins.txt)/coredhcp.go
+popd
+
+gofmt -w $generated
+diff -u $generated cmds/coredhcp/main.go