Fix available faceted searches computation when the default faceted search is identical

Steps to reproduce:

1. define 2 new faceted searches : filterA and filterB
2. navigate to Sections and under Manage > Local Configuration > Faceted search selection, only enable "Defaut search" and "filterA". Save.
3. navigate to Workspaces and Manage > Local Configuration > Faceted search selection, only enable "Defaut search" and "filterB". Save.
4. Log out and log in
5. Switch to faceted search view and check you have 3 filters: "Defaut search", "filterA" and "filterB". And "Defaut search" is selected
6. Navigate to Sections: the 3 filters are still there and "Defaut search" is selected.
   => Only Defaut search" and "filterA" should be present.
7. Navigate to Workspaces: the 3 filters are still there and "Defaut search" is selected.
   => Only Defaut search" and "filterB" should be present.