Echo CAVP comments in the output.

Comments in CAVP are semantically important and we need to copy them
from the input to the output.

Change-Id: Ib798c4ad79de924487d0c4a0f8fc16b757e766d8
Reviewed-on: https://boringssl-review.googlesource.com/16725
Commit-Queue: David Benjamin <davidben@google.com>
Reviewed-by: David Benjamin <davidben@google.com>
CQ-Verified: CQ bot account: commit-bot@chromium.org <commit-bot@chromium.org>

fipstools/cavp_rsa2_keygen_test.cc

diff --git a/fipstools/cavp_rsa2_keygen_test.cc b/fipstools/cavp_rsa2_keygen_test.cc
index a96404d..fa8d658 100644
--- a/fipstools/cavp_rsa2_keygen_test.cc
+++ b/fipstools/cavp_rsa2_keygen_test.cc
@@ -85,11 +85,10 @@
     return 1;
   }
 
-  printf("# Generated by");
-  for (int i = 0; i < argc; i++) {
-    printf(" %s", argv[i]);
-  }
-  printf("\r\n\r\n");
-
-  return FileTestMainSilent(TestRSA2KeyGen, nullptr, argv[1]);
+  FileTest::Options opts;
+  opts.path = argv[1];
+  opts.callback = TestRSA2KeyGen;
+  opts.silent = true;
+  opts.comment_callback = EchoComment;
+  return FileTestMain(opts);
 }