Flip SSL_SESSION fields to bool.

Change-Id: I0a3648437f78f37a4b710aaea73084a19be607c5
Reviewed-on: https://boringssl-review.googlesource.com/29485
Reviewed-by: Adam Langley <agl@google.com>
Commit-Queue: Adam Langley <agl@google.com>
CQ-Verified: CQ bot account: commit-bot@chromium.org <commit-bot@chromium.org>
diff --git a/ssl/tls13_server.cc b/ssl/tls13_server.cc
index 81d78fa..481dc54 100644
--- a/ssl/tls13_server.cc
+++ b/ssl/tls13_server.cc
@@ -168,7 +168,7 @@
     if (!RAND_bytes((uint8_t *)&session->ticket_age_add, 4)) {
       return 0;
     }
-    session->ticket_age_add_valid = 1;
+    session->ticket_age_add_valid = true;
     if (ssl->enable_early_data) {
       session->ticket_max_early_data = kMaxEarlyDataAccepted;
     }