remove some hardcoded 'localhost's from dev environment (#14801)

Trying to use a local test hostname other than localhost
(e.g. discourse.test )for discourse development was difficult due
the fact that localhost was hardcoded in a few places. This patch
uses existing environment variables to allow a developer to use a
different domain when developing.

Signed-off-by: Ryan Lerch <rlerch@redhat.com>

bin/ember-cli

@@ -5,14 +5,14 @@ require 'pathname'
 
 RAILS_ROOT = File.expand_path("../../", Pathname.new(__FILE__).realpath)
 PORT = ENV["UNICORN_PORT"] ||= "3000"
-
+HOSTNAME = ENV["DISCOURSE_HOSTNAME"] ||= "localhost"
 yarn_dir = File.join(RAILS_ROOT, "app/assets/javascripts/discourse")
 
 PROXY =
   if ARGV.include?("--try")
     "https://try.discourse.org"
   else
-    "http://localhost:#{PORT}"
+    "http://#{HOSTNAME}:#{PORT}"
   end
 
 command =