Add instance to debug log at compute api

Add instance info to 2 debug logs at compute api layer.

Change-Id: Icbe8e45ace74b8bf0282cf6d6dd1ead792532961
docs - Set pbr 'warnerrors' option for doc build

By setting this pbr option in setup.cfg, the doc build will fail in case
of any warnings or errors occur during the build process.

Closes-Bug: #1351350

Change-Id: Id4858062d2aaa4c2fe5b597e40e4e8947f544a4d
Merge "docs - Set pbr 'warnerrors' option for doc build"
Merge "Add instance to debug log at compute api"