Spin in DataTest waiting for connections to be established

As the added comment indicates, The QuicTestConnectAndPing function
locally allocates Secrets for the client and server connection for a
given 0RTT test.  However, it doesn't wait for the connection to be
fully established before deciding the test is successful and returning.
Because the allocation of those Secrets was done with a unique_ptr,
leaving the scope of the function automatically deletes that memory,
which another thread may still be referencing while processing data in
the TLS backend, leading to ASAN errors.

Fix it by ensuring that the connection is fully established prior to
returinging (which implies that the TLS backend has completed filling
out secrets, and dropped any reference to the TlsSecrets pointer

Author: nhorman

src/test/lib/DataTest.cpp

@@ -626,6 +626,27 @@ QuicTestConnectAndPing(
                                 ServerSecret->ClientEarlyTrafficSecret,
                                 ClientSecret->SecretLength));
                         Match = true;
+                        //
+                        // This test dynamically allocates ClientSecrets and ServerSecrets
+                        // as a unique_ptr, which then gets passed and used by the underlying TLS
+                        // backend.  However, this code doesn't wait for the connections to finish
+                        // getting established before exiting.  As such it may occur that another
+                        // thread continues establishing the connection while this function exits,
+                        // which automatically deletes the allcoated memory in the Secrets, leading
+                        // to a potential NULL pointer deref in the TLS backend.  We could shutdown
+                        // the connections here, but given that they're not yet fully established,
+                        // that on occaision fails.  Instead, just spin here for a moment waiting
+                        // for the Client and Server Traffic Secrets to get set, at which point
+                        // we are guaranteed that the TLS backend will drop any reference to the
+                        // TLS pointer, so its safe to delete.
+                        //
+                        while (ClientSecret->IsSet.ClientTrafficSecret0 == 0 ||
+                               ClientSecret->IsSet.ServerTrafficSecret0 == 0 ||
+                               ServerSecret->IsSet.ClientTrafficSecret0 == 0 ||
+                               ServerSecret->IsSet.ServerTrafficSecret0 == 0) {
+                                CxPlatSleep(500); // Sleep for a little bit
+                        }
+
                     }
                 }
                 if (!Match) {