tests: filesink: small refactoring
tests: filesink: small refactoring

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