[Server Manager: Make Server manager multi-tasking]
Closes-Bug: #1396864

Use gevent
Testing
Open multiple client and send requests to server.
All request should return response.

Change-Id: I85ec579818bd468e9d22bf338d1cb9801881270f
Merge "[Server Manager: Make Server manager multi-tasking] Closes-Bug: #1396864" into R2.0