Make sure update functions only take care of the chosen sub-theme

When working on #3066987: Move Autoprefixer browsers gulp-option to .browserslistrc file i encountred the issue that the existing update hooks run for every child theme instead of the one given as argument to the drush command bs-theme-update [target-machine-name].

In the above mentioned issue I already started to pass the argument:

@@ -745,7 +746,7 @@ function _bs_base_theme_run_update_hooks($target_machine_name) {
       $update_function = $theme_name . '_bs_update_' . $version;
       if (function_exists($update_function)) {
         drush_print($version . ' -   ' . strip_tags($description), 2);
-        $update_function();
+        $update_function($target_machine_name);
       }
     }

Now this should be back ported to the last two update hooks, which I do here.

This patch here needs the patch from the mentioned issue applied to work properly!