Fix sticky Travis CI test

this commit removes the webserver block within the box add unit test.
It's not actually needed since the test is just ensuring that if a user
adds a box name as a URL it prints a warning to the user.

test/unit/vagrant/action/builtin/box_add_test.rb

@@ -283,7 +283,7 @@ describe Vagrant::Action::Builtin::BoxAdd, :skip_windows do
     context "with a box name accidentally set as a URL" do
       it "displays a warning to the user" do
         box_path = iso_env.box2_file(:virtualbox)
-        with_web_server(box_path) do |port|
+        port = 9999
 
         box_url_name = "http://127.0.0.1:#{port}/#{box_path.basename}"
         env[:box_name] = box_url_name
@@ -303,13 +303,10 @@ describe Vagrant::Action::Builtin::BoxAdd, :skip_windows do
         subject.call(env)
       end
     end
-    end
 
     context "with a box name containing invalid URI characters" do
       it "should not raise an error" do
         box_path = iso_env.box2_file(:virtualbox)
-        with_web_server(box_path) do |port|
-
         box_url_name = "box name with spaces"
         env[:box_name] = box_url_name
 
@@ -325,7 +322,6 @@ describe Vagrant::Action::Builtin::BoxAdd, :skip_windows do
         subject.call(env)
       end
     end
-    end
 
     context "with URL containing credentials" do
       let(:username){ "box-username" }