tests: make netclientclock test faster and less flaky
tests: make netclientclock test faster and less flaky

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