ghostpad: Only implement the iterate_internal_links function on proxypads
ghostpad: Only implement the iterate_internal_links function on proxypads

ghostpads inherit it from their parent class. Also make it threadsafe.

krieger-od/gstreamer,drothlis/gstreamer,lovebug356/gstreamer,Lachann/gstreamer,justinjoy/gstreamer,Distrotech/gstreamer,justinjoy/gstreamer,collects/gstreamer,drothlis/gstreamer,centricular/gstreamer,ensonic/gstreamer,mparis/gstreamer,cfoch/gstreamer,Lachann/gstreamer,cablelabs/gstreamer,StreamUtils/gstreamer,jpakkane/gstreamer,krieger-od/gstreamer,ylatuya/gstreamer,drothlis/gstreamer,surround-io/gstreamer,ensonic/gstreamer,drothlis/gstreamer,lubosz/gstreamer,surround-io/gstreamer,ensonic/gstreamer,ylatuya/gstreamer,mparis/gstreamer,StreamUtils/gstreamer,StreamUtils/gstreamer,collects/gstreamer,mparis/gstreamer,lubosz/gstreamer,magcius/gstreamer,collects/gstreamer,Distrotech/gstreamer,ahmedammar/platform_external_gst_gstreamer,lubosz/gstreamer,cablelabs/gstreamer,cablelabs/gstreamer,Lachann/gstreamer,Distrotech/gstreamer,jpakkane/gstreamer,ahmedammar/platform_external_gst_gstreamer,lubosz/gstreamer,collects/gstreamer,krichter722/gstreamer,collects/gstreamer,jpxiong/gstreamer,magcius/gstreamer,krichter722/gstreamer,krichter722/gstreamer,magcius/gstreamer,lovebug356/gstreamer,jpxiong/gstreamer,krieger-od/gstreamer,centricular/gstreamer,centricular/gstreamer,shelsonjava/gstreamer,shelsonjava/gstreamer,centricular/gstreamer,surround-io/gstreamer,justinjoy/gstreamer,lubosz/gstreamer,shelsonjava/gstreamer,justinjoy/gstreamer,shelsonjava/gstreamer,magcius/gstreamer,StreamUtils/gstreamer,cfoch/gstreamer,cfoch/gstreamer,Distrotech/gstreamer,jpxiong/gstreamer,lovebug356/gstreamer,lovebug356/gstreamer,mparis/gstreamer,mparis/gstreamer,drothlis/gstreamer,ensonic/gstreamer,krichter722/gstreamer,Lachann/gstreamer,cfoch/gstreamer,ensonic/gstreamer,StreamUtils/gstreamer,Lachann/gstreamer,cablelabs/gstreamer,ahmedammar/platform_external_gst_gstreamer,cablelabs/gstreamer,ahmedammar/platform_external_gst_gstreamer,surround-io/gstreamer,justinjoy/gstreamer,ylatuya/gstreamer,Distrotech/gstreamer,lovebug356/gstreamer,ylatuya/gstreamer,shelsonjava/gstreamer,krieger-od/gstreamer,surround-io/gstreamer,ahmedammar/platform_external_gst_gstreamer,jpakkane/gstreamer,jpakkane/gstreamer,ylatuya/gstreamer,krieger-od/gstreamer,magcius/gstreamer,krichter722/gstreamer,jpxiong/gstreamer,jpakkane/gstreamer,centricular/gstreamer,cfoch/gstreamer,jpxiong/gstreamer