refined failure tests

localtests/datetime-to-timestamp/create.sql

@@ -1,6 +1,6 @@
 drop table if exists gh_ost_test;
 create table gh_ost_test (
-  id int auto_increment,
+  id int unsigned auto_increment,
   i int not null,
   ts0 timestamp default current_timestamp,
   ts1 timestamp,

localtests/fail-fk-parent/expect_failure

@@ -0,0 +1 @@
+Parent-side foreign keys are not supported

localtests/fail-fk/expect_failure

@@ -0,0 +1 @@
+Child-side foreign keys are not supported. Bailing out