Remove INVALID_CALL from mid-handshake error message

[TheJokr]

Mid-handshake errors that occur before certificate verification currently look like this:

TLS handshake failed: cert verification failed - Invalid certificate verification context [WRONG_VERSION_NUMBER]

Despite no certificate even being received yet, the error complains about a failed verification. The cause here is that cert verification failed is only omitted if the verification result is OK. The default in BoringSSL before verification runs is INVALID_CALL, however.

INVALID_CALL is set/returned in these places:

• https://github.com/google/boringssl/blob/44b3df6f03d85c901767250329c571db405122d5/src/ssl/internal.h#L3904
• https://github.com/google/boringssl/blob/44b3df6f03d85c901767250329c571db405122d5/src/ssl/ssl_session.cc#L396
• https://github.com/google/boringssl/blob/44b3df6f03d85c901767250329c571db405122d5/src/ssl/ssl_x509.cc#L713

It is not used anywhere else as a verification result code. To improve the error message, this commit adds INVALID_CALL as a verification result for which no additional error is dislayed.