Fix LP985075, cannot save Patron Acquisition Request form

The form is shown using a dojo EditPane attached to an EditDialog,
however, attaching the pane was done manually, resulting in the dialog
acting improperly and the pane positioned improperly.

Instead, we use dojo's attr method to define the content attribute of
the dialog to be the pane.

Signed-off-by: Steven Chan <schan@sitka.bclibraries.ca>
Signed-off-by: Remington Steed <rjs7@calvin.edu>
Signed-off-by: Ben Shum <bshum@biblio.org>