Reduce code complexity on check_ipv6

modules/post/windows/manage/portproxy.rb

@@ -95,8 +95,7 @@ class Metasploit3 < Msf::Post
 		if ipv6_installed()
 			print_status("IPv6 is already installed.")
 			return true
-		else
-			if not datastore['IPV6_XP']
+		elsif not datastore['IPV6_XP']
 			print_error("IPv6 is not installed. You need IPv6 to use portproxy.")
 			return false
 		else
@@ -110,7 +109,6 @@ class Metasploit3 < Msf::Post
 			return true
 		end
 	end
-	end
 
 	def fw_enable_ports
 		print_status ("Setting port #{datastore['LOCAL_PORT']} in Windows Firewall ...")