MDEV-6247: Merge 10.0-galera to 10.1.

Merged lp:maria/maria-10.0-galera up to revision 3879.

Added a new functions to handler API to forcefully abort_transaction,
producing fake_trx_id, get_checkpoint and set_checkpoint for XA. These
were added for future possiblity to add more storage engines that
could use galera replication.

mysql-test/include/galera_end.inc

@@ -0,0 +1,25 @@
+# galera_end.inc
+# ==============
+#
+# Description
+# -----------
+# Closes the connections opened via include/galera_init.inc
+#
+# Parameters
+# ----------
+# $galera_cluster_size
+#   Number of nodes in the cluster.
+#
+
+--let $_galera_node= $galera_cluster_size
+
+while ($_galera_node)
+{
+  if ($galera_debug)
+  {
+    --echo Disconnecting node_$_galera_node
+  }
+  --disconnect node_$_galera_node
+  --dec $_galera_node
+}
+