chore: Enable memory sanitizer build.

I don't know if this will actually work, or how many of these "fixes" I
need to get msan to be happy on CI. For me locally, it all works fine.
On CI, for some reason it's not fine even though I run in the exact same
docker image as CI.

.circleci/config.yml

@@ -71,8 +71,7 @@ jobs:
     steps:
       - checkout
       - run: rm -rf /src/workspace/c-toxcore/* && mv * /src/workspace/c-toxcore/
-      # TODO(iphydf): Remove "|| true" once this works.
-      - run: cd /src/workspace && bazel test //c-toxcore/auto_tests:lossless_packet_test || true
+      - run: cd /src/workspace && bazel test //c-toxcore/auto_tests:lossless_packet_test
 
   infer:
     working_directory: ~/work

toxcore/DHT.c

@@ -351,9 +351,9 @@ int create_request(const uint8_t *send_public_key, const uint8_t *send_secret_ke
 
     uint8_t *const nonce = packet + 1 + CRYPTO_PUBLIC_KEY_SIZE * 2;
     random_nonce(nonce);
-    uint8_t temp[MAX_CRYPTO_REQUEST_SIZE];
-    memcpy(temp + 1, data, data_length);
+    uint8_t temp[MAX_CRYPTO_REQUEST_SIZE] = {0};
     temp[0] = request_id;
+    memcpy(temp + 1, data, data_length);
     const int len = encrypt_data(recv_public_key, send_secret_key, nonce, temp, data_length + 1,
                                  packet + CRYPTO_SIZE);