[rpc] a bit of clean-up on LifoServiceQueue

I was looking at the code in service queue/pool while troubleshooting
one issue, and I noticed there is some room for a minor clean-up such
as removing unused methods, etc.  This patch takes care of that.

Change-Id: Ibcb0dec8ad165773cb5d50869b979d70f9bf4a79
Reviewed-on: http://gerrit.cloudera.org:8080/21049
Tested-by: Alexey Serbin <alexey@apache.org>
Reviewed-by: Mahesh Reddy <mreddy@cloudera.com>
Reviewed-by: Abhishek Chennaka <achennaka@cloudera.com>
3 files changed