Fix SRT listen endpoint via UDP. #1690

Job	Run time
cygwin64-cache	1m 51s
utest-regression-blackbox-test	9m 28s
multiple-arch-aarch64	22m 37s
multiple-arch-armv7	21m 56s
fast	1s
cygwin64	14m 10s
build-ubuntu20	3m 34s
build-centos7	4m 47s
build-cross-arm	5m 18s
build-ubuntu18	3m 8s
build-ubuntu16	2m 59s
build-cross-aarch64	5m 9s
multiple-arch-amd64	2m 21s
coverage	3m 44s
test-done	1s
	1h 41m 4s

Provide feedback