Check that a mirror write returning an error will cause a reconnect and retry

tests/fakes/dest/hang_after_connect.rb

@@ -8,16 +8,14 @@
 # right error message after the timeout time.
 
 require 'flexnbd/fake_dest'
-include FlexNBD::FakeDest
+include FlexNBD
 
-addr, port = *ARGV
-
-serve_sock = serve( addr, port )
-client_sock = accept( serve_sock, "Client didn't make a connection" )
+server = FakeDest.new( *ARGV )
+client = server.accept( "Client didn't make a connection" )
 
 # Sleep for one second past the timeout (a bit of slop in case ruby
 # doesn't launch things quickly)
 sleep(FlexNBD::MS_HELLO_TIME_SECS + 1)
 
-client_sock.close  if client_sock
-serve_sock.close
+client.close
+server.close