Threading utils implemented

* context.spawn spawns green thread w/ cloned ctx
* context.sleep sleeps using eventlet.sleep
* all eventlet usages has been replaced w/ new util

Implements blueprint thread-utils

Change-Id: I1062ca4ac8e3cc3b1d045cd6a4be89837c41afbc
The tenant_id should not be specified in requests

Change-Id: Icf01ebbcfbfc6ffe6347ca5c6e6e9c4cad767e57
Merge "Threading utils implemented"