Fix deadlock in ApiClient::SendMessage

fixes #6368
Fix another deadlock in ApiClient::SendMessage

refs #6368
Add some missing SSL flags

refs #6368
Revert "Fix deadlock in ApiClient::SendMessage"

This reverts commit 0ac6e97f329b551882f925a009e6efe498ec45c3.
Revert "Fix another deadlock in ApiClient::SendMessage"

This reverts commit a0c09303251d22738f82a9c35a66d327c98699a3.
Another attempt at fixing the API deadlock

fixes #6617
Use openssl-quiet.cnf for icinga2-build-ca

fixes #6620
Change return type for Socket::Pool to bool

refs #6617
Add sni option to http check

fixes #6605

Signed-off-by: Gunnar Beutner <gunnar.beutner@netways.de>