SQL SECURITY DEFINER must enforce reduced rights too, not just additional rights.


mysql-test/r/sp-security.result:
  Test case for BUG#2777: Make sure that SQL SECURITY DEFINER enforces reduced rights.
mysql-test/t/sp-security.test:
  Test case for BUG#2777: Make sure that SQL SECURITY DEFINER enforces reduced rights.
sql/sql_acl.cc:
  Clear rights before changing them in acl_getroot_no_password so that
  reduced rights work too, and take care of db acls as well.