Code cleanup, remove useless import

This is a massive removal of all useless import that are all over the code
and unit tests. There's also some simple dead code removal or move.

Change-Id: Ida1208b47f38e552219e3b909f8d7c4f22ba3273
Signed-off-by: Julien Danjou <julien@danjou.info>
Merge "Code cleanup, remove useless import"