Fix embedded innodb_plugin after 560799eb

wsrep_certification_rules: Define as a weak global symbol.
While there are separate _embedded.a for statically
linked storage engine plugins, there is only one ha_innodb.so
which is supposed to work with both values of WITH_WSREP.

The merge from 10.0-galera introduced a reference to a global
variable that is only defined when the server is built WITH_WSREP.
We must define that symbol as weak global, so that when
a dynamically linked InnoDB or XtraDB is used with the embedded
server (which never includes write-set replication patches),
the variable will be read as 0, instead of causing a failure to
load the InnoDB or XtraDB plugin.

sql/wsrep_mysqld_c.h

@@ -21,6 +21,10 @@ enum enum_wsrep_certification_rules {
     WSREP_CERTIFICATION_RULES_OPTIMIZED
 };
 
-extern ulong wsrep_certification_rules;
+/* This is intentionally declared as a weak global symbol, so that
+the same ha_innodb.so can be used with the embedded server
+(which does not link to the definition of this variable)
+and with the regular server built WITH_WSREP. */
+extern ulong wsrep_certification_rules __attribute__((weak));
 
 #endif /* WSREP_MYSQLD_C_H */

storage/innobase/row/row0ins.cc

@@ -56,6 +56,7 @@ Created 4/20/1996 Heikki Tuuri
 #include "m_string.h"
 
 #ifdef WITH_WSREP
+#include <mysql/service_wsrep.h>
 #include "../../../wsrep/wsrep_api.h"
 #include "wsrep_mysqld_c.h"
 #endif /* WITH_WSREP */
@@ -1645,6 +1646,9 @@ row_ins_check_foreign_constraint(
 				if (check_ref) {
 					err = DB_SUCCESS;
 #ifdef WITH_WSREP
+					if (!wsrep_on(trx->mysql_thd)) {
+						goto end_scan;
+					}
 					enum wsrep_key_type key_type;
 					if (upd_node != NULL) {
 						key_type = WSREP_KEY_SHARED;
@@ -1661,7 +1665,7 @@ row_ins_check_foreign_constraint(
 					}
 
 					err = wsrep_append_foreign_key(
-						thr_get_trx(thr),
+						trx,
 						foreign,
 						rec,
 						check_index,

storage/xtradb/row/row0ins.cc

@@ -56,6 +56,7 @@ Created 4/20/1996 Heikki Tuuri
 #include "m_string.h"
 
 #ifdef WITH_WSREP
+#include <mysql/service_wsrep.h>
 #include "../../../wsrep/wsrep_api.h"
 #include "wsrep_mysqld_c.h"
 #endif /* WITH_WSREP */
@@ -1657,6 +1658,9 @@ row_ins_check_foreign_constraint(
 				if (check_ref) {
 					err = DB_SUCCESS;
 #ifdef WITH_WSREP
+					if (!wsrep_on(trx->mysql_thd)) {
+						goto end_scan;
+					}
 					enum wsrep_key_type key_type;
 					if (upd_node != NULL) {
 						key_type = WSREP_KEY_SHARED;
@@ -1673,7 +1677,7 @@ row_ins_check_foreign_constraint(
 					}
 
 					err = wsrep_append_foreign_key(
-						thr_get_trx(thr),
+						trx,
 						foreign,
 						rec,
 						check_index,