fix issue when closing a uTP connection RC_1_2 backport #3044

Job	Run time
Build (crypto=openssl)	2m 27s
Simulations	3m 17s
Tests (crypto=openssl)	1h 6m 51s
Build (release)	3m 5s
Tests (deprecated-functions=off)	11m 38s
	1h 27m 18s

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