Pass pServerCert->hCertStore for hAdditionalStore argument in CertificateChain

[anbergem]

This is just an application of the changes made in pocoproject/poco#3910

Fixes #578

This is a literal copy from the above mentioned PR and POCO and a simple cherry-pick of that single change.

[CLAassistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution.
_{You have signed the CLA already but the status is still pending? Let us recheck it.}