Packstack Plugins Clean-up

- Deleted unused import
- Pep8 compliance
- Deleted unused variables

Change-Id: I45f135b2467427cd7ee3b5ba32745af2a631458a
Signed-off-by: Gael Chamoulaud <gchamoul@redhat.com>
(cherry picked from commit 3da12069efc9044b8f8f8fd4d4118c406f4fe649)