sipaccount: call SIPStartCall after returning call

Some functions in SIPStartCall can take a long time to return, such
as ICE initialization. This allows the manager to return the callId
in outgoingCall() to the client sooner and so prevents the UI from
freezing.

Change-Id: I87b0c4b5d56f69e087f0117b2b78daa026679aab
Tuleap: #620

src/sip/sipaccount.cpp

@@ -240,8 +240,21 @@ SIPAccount::newOutgoingCall(const std::string& toUrl)
         getSrtpKeyExchange()
     );
 
-    if (not created or not SIPStartCall(call))
+    if (created) {
+        auto shared_this = std::static_pointer_cast<SIPAccount>(shared_from_this());
+        std::weak_ptr<SIPCall> weak_call = call;
+        manager.addTask([shared_this, weak_call] {
+            auto call = weak_call.lock();
+
+            if (not call or not shared_this->SIPStartCall(call)) {
+                RING_ERR("Could not send outgoing INVITE request for new call");
+                call->onFailure();
+            }
+            return false;
+        });
+    } else {
         throw VoipLinkException("Could not send outgoing INVITE request for new call");
+    }
 
     return call;
 }