Skip MYSQL_JSON related tests if the plugin is not compiled

mysql-test/main/mysql_json_table_recreate.test

 --source include/have_utf8.inc
 
+if (!$TYPE_MYSQL_JSON_SO) {
+  skip Need MYSQL_JSON plugin;
+}
+
 --echo #
 --echo # The following test takes 2 tables containing a JSON column and attempts
 --echo # to repair them.

mysql-test/main/mysql_upgrade_mysql_json_datatype.test

@@ -2,6 +2,10 @@
 -- source include/have_working_dns.inc
 -- source include/have_innodb.inc
 
+if (!$TYPE_MYSQL_JSON_SO) {
+  skip Need MYSQL_JSON plugin;
+}
+
 call mtr.add_suppression("Table rebuild required");
 call mtr.add_suppression("is marked as crashed");
 call mtr.add_suppression("Checking");