Run Page: DataGrid's column filters not working

[VallariAg]

A couple of issues on /runs page:

Issue 1: when using DataGrid filter feature on "user" column, search for "vallari" (for example) and pulpito-ng would send a request to https://paddles.front.sepia.ceph.com/runs/user/vallari/. That request will fail and the page would go blank.
Expected behaviour: filtering happens on client side and no extra requests are made to paddles.

Issue 2: using DataGrid filter feature on any other column except "user" doesn't work. When trying to filter on any other column (example "runtime"), the filter box's "Columns" field changes back to "user" immediately and does not allow to filter by any other field.

[VallariAg]

Issue 3: #61