CLI arg "host" has precedence over ENV var "host"

This is a regression from when the server command switched to its own
argument parser, as opposed to Rack's. Rack's argument parser, when
provided with a "host" argument, gives that value precedence over
environment variables.

railties/lib/rails/commands/server/server_command.rb

@@ -188,10 +188,12 @@ def port
         end
 
         def host
-          unless (default_host = options[:binding])
+          if options[:binding]
+            options[:binding]
+          else
             default_host = environment == "development" ? "localhost" : "0.0.0.0"
+            ENV.fetch("HOST", default_host)
           end
-          ENV.fetch("HOST", default_host)
         end
 
         def environment

railties/test/commands/server_test.rb

@@ -139,6 +139,14 @@ def test_host
     end
   end
 
+  def test_argument_precedence_over_environment_variable
+    switch_env "HOST", "1.2.3.4" do
+      args = ["-b", "127.0.0.1"]
+      options = parse_arguments(args)
+      assert_equal "127.0.0.1", options[:Host]
+    end
+  end
+
   def test_records_user_supplied_options
     server_options = parse_arguments(["-p", 3001])
     assert_equal [:Port], server_options[:user_supplied_options]