Disable innodb.innodb_bug38231 in embedded mode

The --send command does not seem to work as expected in that mode.

mysql-test/suite/innodb/t/innodb_bug38231.test

@@ -5,6 +5,11 @@
 
 -- source include/have_innodb.inc
 
+# skip this test in embedded mode because "TRUNCATE TABLE bug38231_1"
+# hangs in that mode waiting for "lock_wait_timeout" although it is
+# preceded by --send
+-- source include/not_embedded.inc
+
 SET storage_engine=InnoDB;
 
 # we care only that the following SQL commands do not crash the server