fix rtc over tcp crash when stop rtc publish. #3649

Job	Run time
multiple-arch-armv7	22m 3s
cygwin64-cache	1m 44s
multiple-arch-aarch64	22m 51s
utest-regression-blackbox-test	9m 35s
cygwin64	14m 47s
fast	1s
build-ubuntu16	3m 15s
build-cross-arm	5m 12s
build-ubuntu18	3m 10s
build-centos7	4m 53s
coverage	3m 27s
multiple-arch-amd64	2m 24s
build-ubuntu20	3m 33s
build-cross-aarch64	5m 7s
test-done	0s
	1h 42m 2s

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