Use Feature's built in library loading to load telnet

This mateches other features such as ssh and zlib to automatically load
a library.

Author: ekohl

lib/puppet/feature/telnet.rb

@@ -2,8 +2,4 @@
 
 require_relative '../../puppet/util/feature'
 
-Puppet.features.add :telnet do
-  require 'net/telnet'
-rescue LoadError
-  false
-end
+Puppet.features.add(:telnet, :libs => %(net/telnet))