Add certificate success check

Signed-off-by: Jerry Yu <jerry.h.yu@arm.com>
diff --git a/tests/ssl-opt.sh b/tests/ssl-opt.sh
index 70b9f4b..9930210 100755
--- a/tests/ssl-opt.sh
+++ b/tests/ssl-opt.sh
@@ -8831,6 +8831,7 @@
             -c "server hello, chosen ciphersuite: ( 1301 ) - TLS1-3-AES-128-GCM-SHA256" \
             -c "ECDH curve: x25519"         \
             -c "=> ssl_tls1_3_process_server_hello" \
+            -c "Certificate verification flags clear" \
             -c "<= parse encrypted extensions"
 
 requires_gnutls_tls1_3
@@ -8860,6 +8861,7 @@
             -c "server hello, chosen ciphersuite: ( 1301 ) - TLS1-3-AES-128-GCM-SHA256" \
             -c "ECDH curve: x25519"         \
             -c "=> ssl_tls1_3_process_server_hello" \
+            -c "Certificate verification flags clear" \
             -c "<= parse encrypted extensions"
 
 # Test heap memory usage after handshake