fio: consolidate rand_seed to uint64_t

csscope showed rand_seed was defined 4 times - each a different type.
While they are used differently, the places where they overlap
should reference the same type. This patch makes three of them the same
as suggested by Jens Axboe.

Signed-off-by: Grant Grundler <grundler@chromium.org>

Updated by me to change rand_seed option to unsigned long long
and changes related to that.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/ioengine.h b/ioengine.h
index 949af91..0756bc7 100644
--- a/ioengine.h
+++ b/ioengine.h
@@ -56,7 +56,7 @@
 	/*
 	 * Initial seed for generating the buffer contents
 	 */
-	unsigned long rand_seed;
+	uint64_t rand_seed;
 
 	/*
 	 * IO engine state, may be different from above when we get