Fix ambigious table error for INSERT..SELECT..UPDATE


mysql-test/r/insert_update.result:
  Bug#8147
    Alter test for bug
mysql-test/t/insert_update.test:
  Bug#8147
    Alter test for bug
sql/sql_parse.cc:
  Bug#8147
    Change order of code - 
    skip insert table before calling mysql_prepare_insert()