core/info: make version request more forgiving

Instead of doing too many commands at once, we only do one at a time,
and don't immediately call ourselves again. We don't want to hold up the
plugins' enable() calls for too long.

Also, we can make the request interval slightly longer.

Signed-off-by: Julian Oes <julian@oes.ch>

src/mavsdk/core/system_impl.cpp

@@ -504,8 +504,8 @@ void SystemImpl::send_autopilot_version_request()
 
     if (fut.get() == MavlinkCommandSender::Result::Unsupported) {
         _old_message_520_supported = false;
-        LogWarn() << "Trying alternative command (512).";
-        send_autopilot_version_request();
+        LogWarn()
+            << "Trying alternative command REQUEST_MESSAGE instead of REQUEST_AUTOPILOT_CAPABILITIES next.";
     }
 }
 

src/mavsdk/plugins/info/info_impl.cpp

@@ -52,7 +52,7 @@ void InfoImpl::enable()
 {
     // We're going to retry until we have the version.
     _system_impl->add_call_every(
-        [this]() { _system_impl->send_autopilot_version_request(); }, 1.0f, &_call_every_cookie);
+        [this]() { _system_impl->send_autopilot_version_request(); }, 2.0f, &_call_every_cookie);
 
     if (!_flight_info_subscriptions.empty()) {
         // We're hoping to get flight information regularly to update flight time.