downgrade a warning

this case can now legitimately happen, if you have a cached v2 status
from moria1, and you run with the new list of dirservers that's missing
the old moria1. it's nothing to worry about; the file will die off in
a month or two.

src/or/routerlist.c

@@ -4145,7 +4145,7 @@ update_router_descriptor_cache_downloads_v2(time_t now)
       pds_flags |= PDS_NO_EXISTING_SERVERDESC_FETCH; /* XXXX ignored*/
 
     if (!ds) {
-      log_warn(LD_BUG, "Networkstatus with no corresponding authority!");
+      log_info(LD_DIR, "Networkstatus with no corresponding authority!");
       continue;
     }
     if (! smartlist_len(dl))