Merge pull request #18 from Prabhjot-Sethi/master

Avoid sending delete for a flow entry if index is invalid.
Use seq. num instead of wait_tree lookup to identify the processing queue for netlink ACK (UVE or KSYNC).
Avoiding  tree find and mutex lock in asio context.

Seq. numbers are split between UVE and KSYNC such that all even seq. numbers are used by UVE and odd by KSYNC.