Fixed untracked issue discovered during impl.

- Client side fails with NPE when a response contains non-standard HTTP status code.
- Server side does not work with Response instances returned by client API or contained in exceptions thrown by client API.

Change-Id: I62295c86e1a8739897bb854efb268d5f7100c26d
Signed-off-by: Marek Potociar <marek.potociar@oracle.com>