Force reload of /etc/resolv.conf on WebSession init

Since #5862 we recreate the aiohttp WebSession to force reload
/etc/resolv.conf. However, since aiohttp 3.12.0 (first shipped with
Supervisor 2025.05.4) aiohttp no longer initializes a separate
DNSResolver instance (aio-libs/aiohttp#10897)
for each WebSession. This rendered #5862 essentially useless.

Force a separate DNSResolver isntance to force /etc/resolv.conf
reread.

Note: The automatic reload of /etc/resolv.conf doesn't work in our
case since /etc is stored on a overlayfs. Inotify isn't working in
this case.

Author: agners

supervisor/coresys.py

@@ -124,7 +124,10 @@ async def init_websession(self) -> None:
 
         resolver: aiohttp.abc.AbstractResolver
         try:
-            resolver = aiohttp.AsyncResolver(loop=self.loop)
+            # Use "unused" kwargs to force dedicated resolver instance. Otherwise
+            # aiodns won't reload /etc/resolv.conf which we need to make our connection
+            # check work in all cases.
+            resolver = aiohttp.AsyncResolver(loop=self.loop, timeout=None)
             # pylint: disable=protected-access
             _LOGGER.debug(
                 "Initializing ClientSession with AsyncResolver. Using nameservers %s",