Always enable MBEDTLS_TEST_HOOKS in TLS 1.3-only test configurations

MBEDTLS_TEST_HOOKS is not supposed to change the behavior of the library, so
it's generally good to have it on in functional tests.

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
diff --git a/tests/configs/tls13-only.h b/tests/configs/tls13-only.h
index 0a22c54..7483f1c 100644
--- a/tests/configs/tls13-only.h
+++ b/tests/configs/tls13-only.h
@@ -22,9 +22,11 @@
  *  limitations under the License.
  */
 
+/* Enable TLS 1.3 and core 1.3 features */
 #define MBEDTLS_SSL_PROTO_TLS1_3
 #define MBEDTLS_SSL_TLS1_3_COMPATIBILITY_MODE
 
+/* Disable TLS 1.2 and 1.2-specific features */
 #undef MBEDTLS_SSL_ENCRYPT_THEN_MAC
 #undef MBEDTLS_SSL_EXTENDED_MASTER_SECRET
 #undef MBEDTLS_SSL_PROTO_TLS1_2
@@ -32,3 +34,6 @@
 #undef MBEDTLS_SSL_DTLS_ANTI_REPLAY
 #undef MBEDTLS_SSL_DTLS_HELLO_VERIFY
 #undef MBEDTLS_SSL_DTLS_CLIENT_PORT_REUSE
+
+/* Enable some invasive tests */
+#define MBEDTLS_TEST_HOOKS