LP1760160: Search bar has a different CSS class when on the home page

LP1760160: Search bar has a different CSS class when on the home page

To test:
1. In templates/opac/css/style.css, add some highly noticeable CSS that
applies to .searchbar-home or an element within .searchbar-home, e.g.
  .searchbar-home .search-box {
    background-color: purple;
    height: 4em;
  }
2. Go to the home page of your public catalog.  The .searchbar-home .search-box CSS
should have taken effect.
3. Go to another page of your public catalog, such as a search results
or login page.  The CSS should not have taken effect here.

Signed-off-by: Jane Sandberg <sandbej@linnbenton.edu>
Signed-off-by: Bill Erickson <berickxx@gmail.com>