decrease verbosity of alts handshaker logs which can happen during cancellation (#29058)

src/core/tsi/alts/handshaker/alts_handshaker_client.cc

@@ -209,13 +209,13 @@ void alts_handshaker_client_handle_response(alts_handshaker_client* c,
   }
   /* TSI handshake has been shutdown. */
   if (alts_tsi_handshaker_has_shutdown(handshaker)) {
-    gpr_log(GPR_ERROR, "TSI handshake shutdown");
+    gpr_log(GPR_INFO, "TSI handshake shutdown");
     handle_response_done(client, TSI_HANDSHAKE_SHUTDOWN, nullptr, 0, nullptr);
     return;
   }
   /* Failed grpc call check. */
   if (!is_ok || status != GRPC_STATUS_OK) {
-    gpr_log(GPR_ERROR, "grpc call made to handshaker service failed");
+    gpr_log(GPR_INFO, "grpc call made to handshaker service failed");
     handle_response_done(client, TSI_INTERNAL_ERROR, nullptr, 0, nullptr);
     return;
   }

src/core/tsi/alts/handshaker/alts_tsi_handshaker.cc

@@ -392,7 +392,7 @@ static void on_handshaker_service_resp_recv(void* arg,
   }
   bool success = true;
   if (error != GRPC_ERROR_NONE) {
-    gpr_log(GPR_ERROR,
+    gpr_log(GPR_INFO,
             "ALTS handshaker on_handshaker_service_resp_recv error: %s",
             grpc_error_std_string(error).c_str());
     success = false;