dashboard: Apply filters more consistently

Applying filters one-at-a-time can lead do broken behavior:

* deselect both the `info` and `error` severity checkboxes
* all reports are correctly hidden
* deselect the `apertis/v2021` channels checkbox
* all the other reports incorrectly show up again, regardless of
  their severity

This is because when applying the updated channels filter the code does
not look at the other active filters.

Tweak the code to always check *all* filters regardless of the one that
has been updated.

Signed-off-by: Emanuele Aina <emanuele.aina@collabora.com>