Set verify_result to failure by default

At initialization, set the verify_result field of the ssl session to
MBEDTLS_X509_VERIFY_NOT_STARTED, rather than 0 as it is by default
currently. This prevents mbedtls_ssl_get_verify_result() from indicating
that certificate verification has passed if it is called prior to the
handshake happening.

Signed-off-by: David Horstmann <david.horstmann@arm.com>

library/ssl_tls.c

@@ -954,6 +954,8 @@ void mbedtls_ssl_transform_init(mbedtls_ssl_transform *transform)
 void mbedtls_ssl_session_init(mbedtls_ssl_session *session)
 {
     memset(session, 0, sizeof(mbedtls_ssl_session));
+    /* Set verify_result to indicate failure by default. */
+    session->verify_result = MBEDTLS_X509_VERIFY_NOT_STARTED;
 }
 
 MBEDTLS_CHECK_RETURN_CRITICAL