MAP: Workaround for missing size values in message data base

Not all messages in the MMS/Email message data bases have
the size/attachment size attribute set.

This causes MAP clients to behave wrongly, e.g. they
request to exclude attachments if the attachments size
is 0. Even for messages which actually have attachments.

The attachment size is the only way for MAP clients to
know if attachments are present, hence the behavior of
the client is not wrong.
bug 17389452

Change-Id: I82cd76bc044601eb6e8b190d0c6fc41b51410a93
Signed-off-by: Casper Bonde <c.bonde@samsung.com>