Bug#28466137 MYSQLADMIN SHUTDOWN DOES NOT WAIT FOR MYSQL TO SHUT DOWN ANYMORE

Post push fix:
 5.6 and 5.7: skip added test for embedded
 5.7+: output has extra prefix

Author: trosten

mysql-test/t/mysqladmin_shutdown.test

@@ -1,3 +1,6 @@
+# Embedded server doesn't support external clients
+--source include/not_embedded.inc
+
 # Supported on platforms with UNIX sockets only
 --source include/not_windows.inc