ztest: memory leaks reported by AddressSanitizer

Leaks reported by using AddressSanitizer, GCC 6.1.0

Direct leak of 4097 byte(s) in 1 object(s) allocated from:
    #1 0x414f73 in process_options cmd/ztest/ztest.c:721

Direct leak of 5440 byte(s) in 17 object(s) allocated from:
    #1 0x41bfd5 in umem_alloc ../../lib/libspl/include/umem.h:88
    #2 0x41bfd5 in ztest_zap_parallel cmd/ztest/ztest.c:4659
    #3 0x4163a8 in ztest_execute cmd/ztest/ztest.c:5907

Signed-off-by: Gvozden Neskovic <[email protected]>
Signed-off-by: Brian Behlendorf <[email protected]>
Closes #4896

cmd/ztest/ztest.c

@@ -726,6 +726,7 @@ process_options(int argc, char **argv)
 			} else {
 				(void) strlcpy(zo->zo_dir, path,
 				    sizeof (zo->zo_dir));
+				free(path);
 			}
 			break;
 		case 'V':
@@ -4702,8 +4703,10 @@ ztest_zap_parallel(ztest_ds_t *zd, uint64_t id)
 		tx = dmu_tx_create(os);
 		dmu_tx_hold_zap(tx, object, B_TRUE, NULL);
 		txg = ztest_tx_assign(tx, TXG_MIGHTWAIT, FTAG);
-		if (txg == 0)
+		if (txg == 0) {
+			umem_free(od, sizeof (ztest_od_t));
 			return;
+		}
 		bcopy(name, string_value, namelen);
 	} else {
 		tx = NULL;