Remove unused method 'string_to_bool' from utils

The method 'string_to_bool' in utils is not used.
Furthermore, if we need this method in the future,
we should use 'bool_from_string' from oslo cliutils
to replace it.

partially implements blueprint common-client-library-2

Change-Id: I21978d389a8721a40e1669351575297ce61a438e
Add support for build info API

Add new command to interact with the build info API and return build
revision information.

Closes-Bug: #1267586
Change-Id: Iea501cea4ddfd0a9f463299f71b72795a93e4def
Updated from global requirements

Change-Id: If173908ddb06a946f68fd27db1248f4974033c8c
Merge "Remove unused method 'string_to_bool' from utils"
Merge "Updated from global requirements"
Merge "Add support for build info API"
Pass empty dict not None for empty environment

The server rejects any request with a None environment, so pass an
empty dict not None (we should probably also make the server more
robust so it can cope with None, but this seems the quickest and
most backwards compatible fix for now)

Change-Id: I0c3e8cd14faf257528be2254070bc40821675431
Closes-Bug: #1273993