MDEV-9039 Can't upgrade MariaDB to to 10.1.8 version from 10.0.21

Don't mark the SEQUENCE engine as XA-capable. The engine never
registers itself for any transaction, so it doesn't matter
whether it is XA-capable or not. The only effect of being
"XA-capable" is breaking the "number of XA-capable engines"
check of TC_LOG_MMAP.

storage/sequence/mysql-test/sequence/simple.result

@@ -3,7 +3,7 @@ ENGINE	SEQUENCE
 SUPPORT	YES
 COMMENT	Generated tables filled with sequential values
 TRANSACTIONS	YES
-XA	YES
+XA	NO
 SAVEPOINTS	YES
 set sql_quote_show_create=0;
 show create table seq_1_to_15_step_2;

storage/sequence/sequence.cc

@@ -483,7 +483,7 @@ static int init(void *p)
   hton->create= create_handler;
   hton->discover_table= discover_table;
   hton->discover_table_existence= discover_table_existence;
-  hton->commit= hton->rollback= hton->prepare=
+  hton->commit= hton->rollback=
    (int (*)(handlerton *, THD *, bool)) &dummy_ret_int;
   hton->savepoint_set= hton->savepoint_rollback= hton->savepoint_release=
    (int  (*)(handlerton *, THD *, void *)) &dummy_ret_int;