queue2: fix the buffering-left in the buffering message
queue2: fix the buffering-left in the buffering message

The buffering-left field in the buffering message should contain a time estimate
in milliseconds about for long the buffering is going to take. We can calculate
this value when we do rate_estimates.

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