name as existing view

When trying to create a table with the same name as existing view with
join, mysql server crashes.

The problem is when create table is issued with the same name as view, while
verifying with the existing tables, we assume that base table object is 
created always.

In this case, since it is a view over multiple tables, we don't have the 
mysql derived table object.

Fixed the logic which checks if there is an existing table to not to assume
that table object is created when the base table is view over multiple 
tables.