communicators/winrm: silence warnings loading winrm

/cc @sneal - I silenced warnings using the built-in util. Also, can you
see if we load here if that load error goes away?

plugins/communicators/winrm/plugin.rb

@@ -26,10 +26,18 @@ module VagrantPlugins
 
       def self.init!
         return if defined?(@_init)
+        @_init = true
+
+        # Setup the I18n
         I18n.load_path << File.expand_path(
           "templates/locales/comm_winrm.yml", Vagrant.source_root)
         I18n.reload!
-        @_init = true
+
+        # Load the WinRM gem
+        require "vagrant/util/silence_warnings"
+        Vagrant::Util::SilenceWarnings.silence! do
+          require "winrm"
+        end
       end
     end
   end

plugins/communicators/winrm/shell.rb

@@ -1,9 +1,13 @@
 require "timeout"
 
 require "log4r"
-require "winrm"
 
 require "vagrant/util/retryable"
+require "vagrant/util/silence_warnings"
+
+Vagrant::Util::SilenceWarnings.silence! do
+  require "winrm"
+end
 
 module VagrantPlugins
   module CommunicatorWinRM