notifications: fix multiple conversation requests

We might receive multiple requests, but they are usually
ignored if the conversation already exists. However,
if we load only one conversation, we cannot verify whether
the conversation has already been created. This patch adds
all conversation IDs to the map so that they can be verified.
It also loads convInfos, to verify requests that were accepted
but not synchronized.

Change-Id: Id691be171acc38b256181d58e3e1e41f11a241f9