fix rtc over tcp crash when stop rtc publish. #3648

Job	Run time
cygwin64-cache	1m 54s
multiple-arch-armv7	22m 4s
multiple-arch-aarch64	22m 41s
utest-regression-blackbox-test	9m 37s
fast	1s
cygwin64	14m 57s
build-ubuntu16	3m 7s
build-centos7	4m 55s
build-cross-arm	5m 16s
build-cross-aarch64	5m 16s
build-ubuntu20	3m 31s
coverage	3m 44s
build-ubuntu18	3m 13s
multiple-arch-amd64	2m 24s
test-done	1s
	1h 42m 41s

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