sdkext/cases/devtool: pass a logger to HTTPService

Pass our logger to the HTTPService instance so we can see the requests
and any errors.

Signed-off-by: Ross Burton <ross.burton@arm.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
(cherry picked from commit 3485df2f)
Signed-off-by: Steve Sakoman <steve@sakoman.com>