MDEV-9214 Server miscalculates the number of XA-capable engines

Relax the number-of-XA-engines check on recovery. Allow *more*
engines to be present than absolutely necessary, extra engines
cannot affect ACID guarantees of the recovery process.

As a bonus, 10.0->crash->10.1 upgrade won't complain about
wsrep being a new XA storge engine.

Author: vuvova

sql/log.cc

@@ -9173,12 +9173,10 @@ int TC_LOG_MMAP::recover()
     the first byte after magic signature is set to current
     number of storage engines on startup
   */
-  if (data[sizeof(tc_log_magic)] != total_ha_2pc)
+  if (data[sizeof(tc_log_magic)] > total_ha_2pc)
   {
     sql_print_error("Recovery failed! You must enable "
-                    "exactly %d storage engines that support "
-                    "two-phase commit protocol",
-                    data[sizeof(tc_log_magic)]);
+                    "all engines that were enabled at the moment of the crash");
     goto err1;
   }
 

storage/tokudb/mysql-test/tokudb_mariadb/r/xa-recovery-9214.result

@@ -0,0 +1,6 @@
+select 1;
+1
+1
+select 1;
+1
+1

storage/tokudb/mysql-test/tokudb_mariadb/t/xa-recovery-9214.opt

@@ -0,0 +1 @@
+--disable-tokudb

storage/tokudb/mysql-test/tokudb_mariadb/t/xa-recovery-9214.test

@@ -0,0 +1,16 @@
+#
+# MDEV-9214 Server miscalculates the number of XA-capable engines
+#
+--source include/have_xtradb.inc
+
+select 1;
+
+--exec echo "wait" > $MYSQLTEST_VARDIR/tmp/mysqld.1.expect
+--shutdown_server 0
+--source include/wait_until_disconnected.inc
+
+--exec echo "restart:--enable-tokudb" > $MYSQLTEST_VARDIR/tmp/mysqld.1.expect
+--enable_reconnect
+--source include/wait_until_connected_again.inc
+
+select 1;