Fixes encoding issues for nova api req body.

* Ensure utf-8 encoding for POST/PUT body for api requests
* As per https://wiki.openstack.org/wiki/Encoding.

Fixes bug #1180344

Change-Id: Iea0f16b0c024795fb3aee1cd38bb54ee9da6d90d
Merge "Fixes encoding issues for nova api req body."