Bug 38183: Get the active tab number from data-attribute

Bug 38183: Get the active tab number from data-attribute

To test:

1. Have more than 1 staff member who can manage suggestions
2. Create some suggestions
3. Move some suggestions to different statuses (Pending/Accepted/Rejected) so you have multiple tabs on the "Suggestions management" page.
4. Go to the first tab, check some suggestions, and click "Select manager" under "Update manager".
5. Pick a new manager, notice nothing changes on that tab.
6. Now look at the last tab in your list of tabs, see the suggestion manager has been set incorrectly to the last tab.
7. APPLY PATCH
8. Try 4-5 again. The manager should be selected correctly.
9. Try setting the manaager from every tab, making sure it works right.

Signed-off-by: Phil Ringnalda <phil@chetcolibrary.org>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Katrin Fischer <katrin.fischer@bsz-bw.de>