conversations: do not remove all syncing conversation if remove self

If a ContactRemoved event occured while some conversations were in
a syncing state, the conversations were removed.
This can cause random conversation deletion when importing a JAMS
account who already deleted itself as a contact.
The correct condition was just checked when the conversation is
already cloned.

Change-Id: I378f765480dcd92c7315579ba5c26a4ca50ddb23