gcode_apis: handle restart exceptions

It is expected that the Klippy will disconnect when a restart request is sent.  Handle those exceptions so they return an acknowledgement.

Signed-off-by:  Eric Callahan <arksine.code@gmail.com>

moonraker/plugins/gcode_apis.py

@@ -58,10 +58,20 @@ class GCodeAPIs:
         return await self._send_gcode(script)
 
     async def gcode_restart(self, path, method, args):
-        return await self._send_gcode("RESTART")
+        return await self._do_restart("RESTART")
 
     async def gcode_firmware_restart(self, path, method, args):
-        return await self._send_gcode("FIRMWARE_RESTART")
+        return await self._do_restart("FIRMWARE_RESTART")
+
+    async def _do_restart(self, gc):
+        try:
+            result = await self._send_gcode(gc)
+        except self.server.error as e:
+            if str(e) == "Klippy Disconnected":
+                result = "ok"
+            else:
+                raise
+        return result
 
 def load_plugin(config):
     return GCodeAPIs(config)