Fix dependencies for install_docker_engine state

Summary:
Strangely, on Equatower, pkg is executed before file
for the install_docker_engine state.

This change explicitly sets the order to use.

Test Plan: salt equatower state.apply roles/paas-docker/docker

Reviewers: dereckson

Reviewed By: dereckson

Differential Revision: https://devcentral.nasqueron.org/D1398