agent: Make vhci-hcd Driver Optional

Don't try to load the vhci-hcd Kernel module, when calling `not-my-board
status`. The Kernel module is only necessary when the user tries to
attach a USB device.

not_my_board/_agent.py

@@ -74,8 +74,8 @@ async def get_places(self):
         return [models.Place(**p) for p in response["places"]]
 
     @staticmethod
-    async def usbip_refresh_status():
-        await usbip.refresh_vhci_status()
+    def usbip_refresh_status():
+        usbip.refresh_vhci_status()
 
     @staticmethod
     def usbip_is_attached(vhci_port):
@@ -231,7 +231,7 @@ async def list(self):
         ]
 
     async def status(self):
-        await self._io.usbip_refresh_status()
+        self._io.usbip_refresh_status()
 
         return [
             {

not_my_board/_usbip.py

@@ -301,11 +301,12 @@ def detach(vhci_port):
         detach_path.write_text(f"{vhci_port}")
 
 
-async def refresh_vhci_status():
-    await _ensure_vhci_hcd_driver_available()
+def refresh_vhci_status():
+    vhci_path = pathlib.Path("/sys/devices/platform/vhci_hcd.0")
+    if not vhci_path.exists():
+        return
 
     def status_paths():
-        vhci_path = pathlib.Path("/sys/devices/platform/vhci_hcd.0")
         # the first status path doesn't have a suffix
         status_path = vhci_path / "status"
         count = itertools.count(1)