Ensure --cover works on umbrella apps

Author: José Valim

lib/mix/lib/mix/tasks/test.ex

@@ -6,17 +6,13 @@ defmodule Mix.Tasks.Test do
       Mix.shell.info "Cover compiling modules ... "
       :cover.start
       :cover.compile_beam_directory(compile_path |> to_char_list)
+      output = opts[:output]
 
-      if :application.get_env(:cover, :started) != {:ok, true} do
-        :application.set_env(:cover, :started, true)
-        output = opts[:output]
-
-        fn() ->
-          Mix.shell.info "\nGenerating cover results ... "
-          File.mkdir_p!(output)
-          Enum.each :cover.modules, fn(mod) ->
-            :cover.analyse_to_file(mod, '#{output}/#{mod}.html', [:html])
-          end
+      fn() ->
+        Mix.shell.info "\nGenerating cover results ... "
+        File.mkdir_p!(output)
+        Enum.each :cover.modules, fn(mod) ->
+          :cover.analyse_to_file(mod, '#{output}/#{mod}.html', [:html])
         end
       end
     end