Bug 33506: Fix false index for series and keep selected index on scan index page

Bug 33506: Fix false index for series and keep selected index on scan index page

The pull down with search options had the wrong index
linked to the Series entry: su instead of se

To test:
* Go to advanced search in staff interface
* Activate 'More options'
* Check checkbox for scan indexes
* Switch to author (especially when using Elasticsearch)
* Search for C
* Verify search results link to authors using c
* Switch to series
* Verify search results use 'su' for subject
* Verify that search option pull down always jumps back to first
  entry: Any word
* Apply patch
* Verify the search results for series now use correct index se
* Verify that coming from advanced search, the correct search option is selected
* Verify that changing the search option also keeps the selection after searching

Note: with Elasticsearch and default configuration author, title and series will
give you results.

Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>