iolog: fix Error handling issues (NEGATIVE_RETURNS)

CID 494151: Error handling issues (NEGATIVE_RETURNS) @ io_u.c:1877 in get_io_u()
This patch removes negative returns from dp_init() to ensure
its value can be properly consumed by td_verror()

Signed-off-by: Hyunwoo Park <dshw.park@samsung.com>

iolog.c

@@ -145,7 +145,7 @@ static int ipo_special(struct thread_data *td, struct io_piece *ipo)
 				int dp_init_ret = dp_init(td);
 
 				if (dp_init_ret != 0) {
-					td_verror(td, dp_init_ret, "dp_init");
+					td_verror(td, abs(dp_init_ret), "dp_init");
 					return -1;
 				}
 			}