Add docker-common package to be removed before installation

[lukas-bednar]

Fixes issue on CentOS systems, with docker-ce-18.03.1

Transaction check error:
  file /usr/bin/docker from install of docker-ce-18.03.1.ce-1.el7.centos.x86_64 conflicts with file from package docker-common-2:1.13.1-53.git774336d.el7.centos.x86_64
  file /usr/bin/docker-containerd from install of docker-ce-18.03.1.ce-1.el7.centos.x86_64 conflicts with file from package docker-common-2:1.13.1-53.git774336d.el7.centos.x86_64
  file /usr/bin/docker-containerd-shim from install of docker-ce-18.03.1.ce-1.el7.centos.x86_64 conflicts with file from package docker-common-2:1.13.1-53.git774336d.el7.centos.x86_64
  file /usr/bin/dockerd from install of docker-ce-18.03.1.ce-1.el7.centos.x86_64 conflicts with file from package docker-common-2:1.13.1-53.git774336d.el7.centos.x86_64

Signed-off-by: Lukas Bednar lbednar@redhat.com

[paulfantom]

LGTM