Revert "sip: set incoming call secure state"

This reverts commit 1e249e4f.

The idea is "good" in theory, but the implementation of
setSecure() causes an exception error.
We need to find a better solution.

Change-Id: I4062388782c07ba3d5a9ab8eb9df655be676d9e4

src/sip/sipvoiplink.cpp

@@ -294,7 +294,6 @@ transaction_request_cb(pjsip_rx_data *rdata)
         }
     }
     call->setTransport(transport);
-    call->setSecure(transport->isSecure());
 
     // FIXME : for now, use the same address family as the SIP transport
     auto family = pjsip_transport_type_get_af(pjsip_transport_get_type_from_flag(transport->get()->flag));