InstallabilityTester: Update the pseudo-essential cache when we remove a "choice" too

When we're removing choice, we need to look into all the choice groups
and invalidate the cache if it's in there.

britney2/installability/tester.py

@@ -163,7 +163,9 @@ class InstallabilityTester(object):
 
         if pkg_id in self._suite_contents:
             self._suite_contents.remove(pkg_id)
-            if pkg_id.architecture in self._cache_ess and pkg_id in self._cache_ess[pkg_id.architecture][0]:
+            if pkg_id.architecture in self._cache_ess:
+                (start, ess_never, ess_choices) = self._cache_ess[pkg_id.architecture]
+                if pkg_id in start or any([pkg_id in choices for choices in ess_choices]):
                     # Removes a package from the "pseudo-essential set"
                     del self._cache_ess[pkg_id.architecture]