[TODO] Force the socket closing in M2SSLTransport

[chaen]

m2Crypto's socket closing is not optimal to say the least.
I've reported the issue (https://gitlab.com/m2crypto/m2crypto/-/issues/278) and done the MR upstream (https://gitlab.com/m2crypto/m2crypto/-/merge_requests/247)
In the meantime, I have implemented mitigation, but it is not bullet proof (#4642)

Once this get merged, we should use that

[fstagni]

I guess this can be closed now...? @chaen can you confirm?

[chaen]

yep