tests: added tests for multiple ticket reception

This introduces tests for the reception (parsing) of multiple tickets by a gnutls client. It uses the tlslite-ng server because unlike a gnutls server, tlslite-ng does send multiple tickets in a single record. That way we test that we can parse both ways of sending tickets. The test is placed in suite/ because it depends on tlslite submodule.

Checklist

• Test suite updated with functionality tests

Reviewer's checklist:

• Any issues marked for closing are addressed
• There is a test suite reasonably covering new functionality or modifications
• Function naming, parameters, return values, types, etc., are consistent and according to CONTRIBUTION.md
• This feature/change has adequate documentation added
• No obvious mistakes in the code