LP#1314902: Restore header bar styles on results pages

Commit fc99f4f2 made an incomplete style change, changing
'results_header_bar' to be a class, but not changing the CSS.  The
simplest solution is to restore 'results_header_bar' to be an id, as
this fixes the main view, the responsive view, and also any custom CSS
which might affect this id.

Signed-off-by: Dan Wells <dbw2@calvin.edu>
Signed-off-by: Remington Steed <rjs7@calvin.edu>
Signed-off-by: Galen Charlton <gmc@esilibrary.com>