Cleanup in wp_admin_bar_new_content_menu. current() instead of array_shift(),...

Cleanup in wp_admin_bar_new_content_menu. current() instead of array_shift(), remove unused index 1 from the arrays, remove ?post_type=post from the Post link. see #18197.

git-svn-id: https://core.svn.wordpress.org/trunk@18788 1a063a9b-81f0-0310-95a4-ce76da25c4cd