Don't try to install last docker-ce version on CentOS

Summary:
Could conflict with containerd.io, provided by another repo.

Fixes the following issue:

Error:
 Problem: package docker-ce-3:19.03.6-3.el7.x86_64 requires containerd.io >= 1.2.2-3, but none of the providers can be installed
  - cannot install the best candidate for the job
(try to add '--skip-broken' to skip uninstallable packages or '--nobest' to use not only best candidate packages)

Ref T1595.

Test Plan: salt-call state.sls_id install_docker_engine roles/paas-docker/docker/software

Reviewers: dereckson

Reviewed By: dereckson

Maniphest Tasks: T1595

Differential Revision: https://devcentral.nasqueron.org/D2213