removeContact: actually close all channels not only SIP

Removing a contact was not actually closing all connections, causing
the remote contact to be able to call even if it was banned if there
was more than two channels opened.
Rewrite closeConnectionsWith as it was unused to use it to close
connections with the banned contact.

jami-project#1449

Change-Id: I147f437370a553f0682b0cea060720a6c473f8a2