Require docker class rather than 'docker' package.
Require docker class rather than 'docker' package.

The docker package in Ubuntu is a GUI dock utility rather than the Docker
container engine.  Relying on the class for squidinacan to function will give
us the desired result and eliminates the installation of a spurious package.

ros-infrastructure/buildfarm_deployment,ros-infrastructure/buildfarm_deployment,ros-infrastructure/buildfarm_deployment,clearpathrobotics/buildfarm_deployment,clearpathrobotics/buildfarm_deployment,ros-infrastructure/buildfarm_deployment,clearpathrobotics/buildfarm_deployment