net: set clock name in the constructor
net: set clock name in the constructor

gst_net_client_clock_new() and gst_ntp_clock_new() didn't set the
"name" property.

https://bugzilla.gnome.org/show_bug.cgi?id=775538

StreamUtils/gstreamer,StreamUtils/gstreamer,StreamUtils/gstreamer,StreamUtils/gstreamer,StreamUtils/gstreamer