Fix error log of proxy-server when cache middleware is disabled

Change-Id: I0b67721cbb692fb8d2a5dd8b2c4f5383512b7b45
Closes-Bug: #1306591
Fix redundant add operation of set in ring

You don't need to add dev_id into seen_ids again when it has already existed in seen_ids.

Fixes Bug #1311190

Change-Id: If0766de8dc5e2a59a648cae39c789c91131805d2
Merge "Fix redundant add operation of set in ring"
Merge "Fix error log of proxy-server when cache middleware is disabled"