webrtc: Fix memory leak in icestream
Since both g_value_set_object() and g_weak_ref_get() takes a reference there will be two new references to the GstWebRTCICE object when there should be only one. g_value_take_object() has the same functionality as g_value_set_object() but does not take a reference.
Without this change, the GstWebRTCICE object will be leaked.