Fix issue with port forwarding not respecting protocol option.

lib/vagrant/action/vm/forward_ports.rb

@@ -125,6 +125,7 @@ module Vagrant
           port.name = name
           port.guestport = options[:guestport]
           port.hostport = options[:hostport]
+          port.protocol = options[:protocol] || :tcp
           @env["vm"].vm.network_adapters[options[:adapter]].nat_driver.forwarded_ports << port
         end
       end

lib/vagrant/config/vm.rb

@@ -35,7 +35,7 @@ module Vagrant
         options = {
           :guestport  => guestport,
           :hostport   => hostport,
-          :protocol   => "TCP",
+          :protocol   => :tcp,
           :adapter    => 0,
           :auto       => false
         }.merge(options || {})