Remove the code that alters the wp_admin_bar_render hooks.

[johnbillion]

The code that alters the hooks for the admin bar is redundant and causes the admin bar to be processed twice on the "Install Required Plugins" screen.

The following two lines are erroneous because wp_admin_bar_render hasn't been hooked to admin_footer since WordPress 3.4 (Trac ticket #20161).

remove_action( 'admin_footer', 'wp_admin_bar_render', 1000 );
add_action( 'admin_head', 'wp_admin_bar_render', 1000 );

This causes wp_admin_bar_render to be hooked twice, once on the default in_admin_header and once on admin_head. The net effect is that the admin bar is processed twice, which causes breakage. An example of this in the wild is my User Switching plugin which throws a notice on this screen due to the node it hooks onto not being available.

Additionally, the following two lines achieve nothing because we're in the admin area so they can be removed too:

remove_action( 'wp_footer', 'wp_admin_bar_render', 1000 );
add_action( 'wp_head', 'wp_admin_bar_render', 1000 );

[thomasgriffin]

Thanks for the PR. Merged!