Bug 18040: Updating buttons in Tools -> Upload local cover image

Bug 18040: Updating buttons in Tools -> Upload local cover image

To test:
1) Go to Tools -> Upload local cover image
2) Select an image and click Upload file
3) Notice Process images button looks different to Upload file button
4) Apply patch and refresh page
5) Follow steps 1-3 again and notice the changed styling of the buttons

Sponsored-by: Catalyst IT
Signed-off-by: Mark Tompsett <mtompset@hotmail.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>