If a view was created with the DEFINER security and later the definer user
was dropped then a SELECT from the view throws the error message saying that
there is no definer user is registered. This is ok for a root but too much
for a mere user.

Now the st_table_list::prepare_view_securety_context() function reveals
the absence of the definer only to a superuser and throws the 'access denied'
error to others.


mysql-test/t/view_grant.test:
  Added a test case for bug#17254: Error for DEFINER security on VIEW provides too much info
mysql-test/r/view_grant.result:
  Added a test case for bug#17254: Error for DEFINER security on VIEW provides too much info
sql/table.cc:
  Bug#17254: Error for DEFINER security on VIEW provides too much info
  Now the st_table_list::prepare_view_securety_context() function reveals
  the absence of the definer only to a superuser and throws the 'access denied'
  error to others.