"optimization cleanup" reverted - problems on rpl_redirect test.

It happens that mysql->client_next->client_next=mysql
and mysql_close() goes into infinite loop.
Results vary from simple sigsegv (FreeBSD), to hard system lockup (Linux)
:)

libmysql/libmysql.c

@@ -2276,6 +2276,8 @@ static MYSQL* spawn_init(MYSQL* parent, const char* host,
   else if (parent->options.db)
     child->options.db = my_strdup(parent->options.db, MYF(0));
 
+  child->options.rpl_parse = child->options.rpl_probe = child->rpl_pivot = 0;
+
   return child;
 }