Remove exceptions from the printer discovery session APIs.

It is not possible for a client to check whether the session is not
closed and add/update/remove printers atomically. It is always possible
that in between the two method calls the session is closed. Therefore,
we cannot enforce the exceptions.

Change-Id: If0e89e4429c4c360515da8f4bbe0ea3781e8e8fd
2 files changed