Fix wrong impl failing IPv4-in-IPv6 when IPv4-mapped IPv6 is missing #190

Job	Run time
Run checks and tests over 22.3 and ubuntu-20.04	2m 22s
Run checks and tests over 22.3 and windows-2019	3m 28s
Run checks and tests over 23.3 and ubuntu-20.04	2m 33s
Run checks and tests over 23.3 and windows-2019	3m 33s
Run checks and tests over 24.3 and ubuntu-20.04	2m 0s
Run checks and tests over 24.3 and windows-2019	3m 3s
Run checks and tests over 25.3 and ubuntu-20.04	1m 59s
Run checks and tests over 25.3 and windows-2019	3m 4s
Run checks and tests over 26.0 and ubuntu-20.04	1m 58s
Run checks and tests over 26.0 and windows-2019	2m 58s
Run checks and tests over 26.1 and ubuntu-20.04	2m 7s
Run checks and tests over 26.1 and windows-2019	2m 57s
Run checks and tests over 26.2 and ubuntu-20.04	1m 52s
Run checks and tests over 26.2 and windows-2019	3m 5s
	36m 59s

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