Renegotiation: Add tests for SigAlg ext parsing
Renegotiation: Add tests for SigAlg ext parsing

This commit adds regression tests for the bug when we didn't parse the
Signature Algorithm extension when renegotiating. (By nature, this bug
affected only the server)

The tests check for the fallback hash (SHA1) in the server log to detect
that the Signature Algorithm extension hasn't been parsed at least in
one of the handshakes.

A more direct way of testing is not possible with the current test
framework, since the Signature Algorithm extension is parsed in the
first handshake and any corresponding debug message is present in the
logs.

NXPmicro/mbedtls,NXPmicro/mbedtls,ARMmbed/mbedtls,Mbed-TLS/mbedtls,Mbed-TLS/mbedtls,Mbed-TLS/mbedtls,Mbed-TLS/mbedtls,NXPmicro/mbedtls,ARMmbed/mbedtls,ARMmbed/mbedtls,ARMmbed/mbedtls,NXPmicro/mbedtls