Post-push fix for BUG#11809016.

In 5.5, REFRESH SLAVE is used as an alias for RESET SLAVE and
was removed in 5.6. Reseting a slave through REFRESH SLAVE was
causing errors in the valgrind platform since reset_slave_info
was undefined.

To fix the problem, we have set reset_slave_info while calling
REFRESH SLAVE.

sql/sql_yacc.yy

@@ -11306,7 +11306,10 @@ flush_option:
         | STATUS_SYM
           { Lex->type|= REFRESH_STATUS; }
         | SLAVE
-          { Lex->type|= REFRESH_SLAVE; }
+          { 
+            Lex->type|= REFRESH_SLAVE;
+            Lex->reset_slave_info.all= false;
+          }
         | MASTER_SYM
           { Lex->type|= REFRESH_MASTER; }
         | DES_KEY_FILE