tests: capsfilter: add test for pending_events pushing
tests: capsfilter: add test for pending_events pushing

make sure that pending events are pushed when caps are already
set when a buffer is received

jpakkane/gstreamer,krichter722/gstreamer,jpxiong/gstreamer,cablelabs/gstreamer,mparis/gstreamer,cfoch/gstreamer,ensonic/gstreamer,StreamUtils/gstreamer,Lachann/gstreamer,krichter722/gstreamer,jpakkane/gstreamer,surround-io/gstreamer,Lachann/gstreamer,jpakkane/gstreamer,centricular/gstreamer,surround-io/gstreamer,shelsonjava/gstreamer,Lachann/gstreamer,Lachann/gstreamer,surround-io/gstreamer,cfoch/gstreamer,krichter722/gstreamer,ensonic/gstreamer,cablelabs/gstreamer,centricular/gstreamer,mparis/gstreamer,mparis/gstreamer,cfoch/gstreamer,ensonic/gstreamer,mparis/gstreamer,StreamUtils/gstreamer,cablelabs/gstreamer,surround-io/gstreamer,StreamUtils/gstreamer,jpxiong/gstreamer,centricular/gstreamer,centricular/gstreamer,mparis/gstreamer,cfoch/gstreamer,ensonic/gstreamer,shelsonjava/gstreamer,jpxiong/gstreamer,jpakkane/gstreamer,cfoch/gstreamer,centricular/gstreamer,shelsonjava/gstreamer,StreamUtils/gstreamer,shelsonjava/gstreamer,krichter722/gstreamer,jpakkane/gstreamer,shelsonjava/gstreamer,surround-io/gstreamer,cablelabs/gstreamer,Lachann/gstreamer,StreamUtils/gstreamer,ensonic/gstreamer,cablelabs/gstreamer,jpxiong/gstreamer,krichter722/gstreamer,jpxiong/gstreamer