manager: shutdown connections before unregistering accounts

shutdownConnections is only called when the account is disabled to
avoid to call it if the account's config is changed.
However, when stopping the daemon, doUnregister is called if the
account is enabled, and this should also call shutdownConnections()
to avoid any lock.

Change-Id: I35fba66b1b7f86360fa29cbeec78697f2b7c3328