Fix UDP acronym

It's 'User', not 'Unreliable'.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/engines/net.c b/engines/net.c
index cf6025f..7354d31 100644
--- a/engines/net.c
+++ b/engines/net.c
@@ -79,7 +79,7 @@
 			  },
 			  { .ival = "udp",
 			    .oval = FIO_TYPE_UDP,
-			    .help = "Unreliable Datagram Protocol",
+			    .help = "User Datagram Protocol",
 			  },
 			  { .ival = "unix",
 			    .oval = FIO_TYPE_UNIX,