[fix] Fix package index selection indexing

Index constructed package indexes by all their parameters.

src/zc/buildout/easy_install.py

@@ -142,7 +142,7 @@ class AllowHostsPackageIndex(setuptools.package_index.PackageIndex):
 
 _indexes = {}
 def _get_index(index_url, find_links, allow_hosts=('*',)):
-    key = index_url, tuple(find_links)
+    key = index_url, tuple(find_links), allow_hosts
     index = _indexes.get(key)
     if index is not None:
         return index