Make Chef omnitruck endpoint configurable

Signed-off-by: Brian Dwyer <Brian.Dwyer@broadridge.com>

Author: bdwyertech

lib/mixlib/install/dist.rb

@@ -7,7 +7,7 @@ class Dist
       # Binary repository base endpoint
       PRODUCT_ENDPOINT = "https://packages.chef.io".freeze
       # Omnitruck endpoint
-      OMNITRUCK_ENDPOINT = "https://omnitruck.chef.io".freeze
+      OMNITRUCK_ENDPOINT = (ENV['CHEF_OMNITRUCK_ENDPOINT'] || "https://omnitruck.chef.io").freeze
       # Default product name
       DEFAULT_PRODUCT = "chef".freeze
       # Default download page URL