Email: Update sync status for mailboxs which not load from server.

For IMAP and POP3 account, there are some mailbox do not load the data
from the server. If the user try to sync them, it also need update the
sync status for these mailboxs to refresh the UI.

CRs-fixed: 652818

Change-Id: Ibcc0b4c29832120d3d9285e93adc143cfb7b1e56