org-agenda.el (org-agenda-bulk-action): Always read the date through `org-read-date'

org-agenda.el (org-agenda-bulk-action): Always read the date through `org-read-date'

* org-agenda.el (org-agenda-bulk-action): Always read the date
through `org-read-date'.  When possible, use the date at point
as the default date.

The previous behavior was trying to mimik the previous behavior
we had with `k m' (to mark the item at point) followed by ̀k s'
(to rescheduled it to the date at point, with no question.)

The current behavior always ask for a date/time interactively,
but takes the date at point as the current date, which makes it
fast enough.

Thanks to Nick Dokos for raising concerns about this.