Reordering taxonomy terms after "Reset to alphabetical" yields incorrect results upon save

Problem/Motivation

The Taxonomy Term List shows terms in unexpected order when re-ordering following a reset to alphabetical order.

Steps to reproduce

1. Do a standard install
2. Log in as admin
3. Add the following tags in this order: Bravo 1, Alpha 2, Delta 3, Charlie 4. (These are the terms the new tests use.)
4. Navigate to the list of tags. You should see them ordered as: Alpha 2, Bravo 1, Charlie 4, Delta 3.
5. Drag Charlie 4 up so it is the second term in the list and Save.
6. The list of tags should be ordered as: Alpha 2, Charlie 4, Bravo 1, Delta 3.
7. Click reset to alphabetical and confirm.
8. The list of tags should be: Alpha 2, Bravo 1, Charlie 4, Delta 3.
9. Drag Charlie 4 up so it is the second term in the list and Save.
10. The list of tags is expected to be ordered as: Alpha 2, Charlie 4, Bravo 1, Delta 3... but they are not ordered as expected.

If you clear cache and refresh the page after step 8 above, then the ordering in the last step is as would be expected.

Proposed resolution

Clear cache as part of resetting to alphabetical order.

Currently there's a function that does a straight-up database query to update weights, with no caches being cleared or invalidated.

Remaining tasks

Review

User interface changes

None

API changes

None

Data model changes

None

Release notes snippet

None