require net/dhcp only when cloudstack hint present

--- ./lib/ohai/mixin/cloudstack_metadata.rb~	2014-12-01 22:01:15.000000000 +0200
+++ ./lib/ohai/mixin/cloudstack_metadata.rb	2014-12-04 17:21:55.363338588 +0200
@@ -17,7 +17,6 @@
 
 require 'ohai/mixin/ec2_metadata'
 require 'ohai/hints'
-require 'net/dhcp'
 require 'socket'
 
 
@@ -30,6 +29,8 @@
         response = ''
         if Ohai::Hints.hint?('cloudstack')
           begin
+			require 'net/dhcp'
+
             request = DHCP::Discover.new
 
             listensock = UDPSocket.new