argb-controlbinding: fix messed up property setter
argb-controlbinding: fix messed up property setter

This was misassigning the control sources. It was also leaking the old values if
a control source would be replaced.

jpakkane/gstreamer,shelsonjava/gstreamer,shelsonjava/gstreamer,ensonic/gstreamer,centricular/gstreamer,surround-io/gstreamer,mparis/gstreamer,lubosz/gstreamer,jpxiong/gstreamer,mparis/gstreamer,surround-io/gstreamer,surround-io/gstreamer,mparis/gstreamer,lubosz/gstreamer,shelsonjava/gstreamer,ensonic/gstreamer,lovebug356/gstreamer,jpxiong/gstreamer,cfoch/gstreamer,krichter722/gstreamer,ensonic/gstreamer,cablelabs/gstreamer,shelsonjava/gstreamer,krieger-od/gstreamer,krieger-od/gstreamer,collects/gstreamer,krieger-od/gstreamer,collects/gstreamer,Lachann/gstreamer,cfoch/gstreamer,lubosz/gstreamer,jpxiong/gstreamer,jpakkane/gstreamer,StreamUtils/gstreamer,StreamUtils/gstreamer,jpakkane/gstreamer,collects/gstreamer,cablelabs/gstreamer,krichter722/gstreamer,justinjoy/gstreamer,mparis/gstreamer,cfoch/gstreamer,StreamUtils/gstreamer,mparis/gstreamer,cablelabs/gstreamer,surround-io/gstreamer,centricular/gstreamer,cfoch/gstreamer,justinjoy/gstreamer,lubosz/gstreamer,krichter722/gstreamer,krichter722/gstreamer,Lachann/gstreamer,justinjoy/gstreamer,StreamUtils/gstreamer,krieger-od/gstreamer,Lachann/gstreamer,StreamUtils/gstreamer,surround-io/gstreamer,jpakkane/gstreamer,centricular/gstreamer,centricular/gstreamer,lovebug356/gstreamer,jpxiong/gstreamer,cablelabs/gstreamer,shelsonjava/gstreamer,krichter722/gstreamer,cablelabs/gstreamer,lubosz/gstreamer,cfoch/gstreamer,ensonic/gstreamer,justinjoy/gstreamer,justinjoy/gstreamer,collects/gstreamer,krieger-od/gstreamer,ensonic/gstreamer,collects/gstreamer,lovebug356/gstreamer,lovebug356/gstreamer,Lachann/gstreamer,lovebug356/gstreamer,jpakkane/gstreamer,centricular/gstreamer,Lachann/gstreamer,jpxiong/gstreamer