mutex: make 0/1 FIO_MUTEX_LOCKED and FIO_MUTEX_UNLOCKED

Makes the API look cleaner.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/init.c b/init.c
index 3865d09..475a6ad 100644
--- a/init.c
+++ b/init.c
@@ -807,7 +807,7 @@
 			f->real_file_size = -1ULL;
 	}
 
-	td->mutex = fio_mutex_init(0);
+	td->mutex = fio_mutex_init(FIO_MUTEX_LOCKED);
 
 	td->ts.clat_percentiles = td->o.clat_percentiles;
 	if (td->o.overwrite_plist)