Use "while ... do" instead of "loop do"

Minor code refactoring.

lib/logstash/outputs/tcp.rb

@@ -150,8 +150,7 @@ def register
         begin
           client_socket = connect unless client_socket
           r,w,e = IO.select([client_socket], [client_socket], [client_socket], nil)
-          loop do
-            break if !r.any?
+          while r.any? do
             # don't expect any reads, but a readable socket might
             # mean the remote end closed, so read it and throw it away.
             # we'll get an EOFError if it happens.