tests: skip legacy qcow2 encryption test if AES is not available

This avoids test breakage when we drop support for using the
built-in AES impl as a fallback for missing crypto libraries.

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>

tests/unit/test-crypto-block.c

@@ -574,6 +574,13 @@ int main(int argc, char **argv)
     for (i = 0; i < G_N_ELEMENTS(test_data); i++) {
         if (test_data[i].open_opts->format == QCRYPTO_BLOCK_FORMAT_LUKS &&
             !qcrypto_hash_supports(test_data[i].hash_alg)) {
+            g_printerr("# skip unsupported %s\n",
+                       QCryptoHashAlgo_str(test_data[i].hash_alg));
+            continue;
+        }
+        if (!qcrypto_cipher_supports(QCRYPTO_CIPHER_ALGO_AES_128,
+                                     QCRYPTO_CIPHER_MODE_CBC)) {
+            g_printerr("# skip unsupported aes-128:cbc\n");
             continue;
         }
         if (!test_data[i].slow ||