Revert "Default repo manifest settings in git config"

This reverts commit ee1c2f5717fcc137ab887a4aae8a08d50a539b9a.

This breaks a lot of buildbot systems. Rolling it back for now
until we can understand what the breakage was and how to fix it.
diff --git a/manifest_xml.py b/manifest_xml.py
index c9e5c40..9189eec 100644
--- a/manifest_xml.py
+++ b/manifest_xml.py
@@ -228,11 +228,7 @@
   @property
   def manifest_server(self):
     self._Load()
-
-    if self._manifest_server:
-      return self._manifest_server
-
-    return self.manifestProject.config.GetString('repo.manifest-server')
+    return self._manifest_server
 
   @property
   def IsMirror(self):