Specific tests fails on non-Linux platforms (affect only main)
After merging the netmgr-v2, the xfer test fails reliably on FreeBSD 11, FreeBSD 12 and macOS. The zero test gets stuck on FreeBSD 11. The ixfr test fails intermittently on FreeBSDs.
The netmgr unit tests fail with dangling socket assertion failure.
These all needs to be investigated, fixed and merged before we can backport the netmgr-v2 to 9.16.