oem: check variant before waiting for apt configuration

because if we add support for variant == 'core' (spoilers!), then apt
may never be configured.

subiquity/server/controllers/oem.py

@@ -69,6 +69,10 @@ def __init__(self, app) -> None:
         self.kernel_configured_event = asyncio.Event()
 
     def start(self) -> None:
+        self._wait_confirmation = asyncio.Event()
+        self.app.hub.subscribe(
+            InstallerChannels.INSTALL_CONFIRMED,
+            self._wait_confirmation.set)
         self._wait_apt = asyncio.Event()
         self.app.hub.subscribe(
             InstallerChannels.APT_CONFIGURED,
@@ -121,8 +125,8 @@ async def wants_oem_kernel(self, pkgname: str,
 
     @with_context()
     async def load_metapackages_list(self, context) -> None:
-        with context.child("wait_apt"):
-            await self._wait_apt.wait()
+        with context.child("wait_confirmation"):
+            await self._wait_confirmation.wait()
 
         # Only look for OEM meta-packages on supported variants and if we are
         # not running core boot.
@@ -138,6 +142,9 @@ async def load_metapackages_list(self, context) -> None:
             self.model.metapkgs = []
             return
 
+        with context.child("wait_apt"):
+            await self._wait_apt.wait()
+
         apt = self.app.controllers.Mirror.final_apt_configurer
         try:
             async with apt.overlay() as d: