contrib: remove unused "rpm" variant of systemd unit

This unit file was created when we packaged rpms without the
socket activation unit, but that's no longer the case.

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

contrib/init/systemd/docker.service.rpm

@@ -1,33 +0,0 @@
-[Unit]
-Description=Docker Application Container Engine
-Documentation=https://docs.docker.com
-After=network-online.target firewalld.service
-Wants=network-online.target
-
-[Service]
-Type=notify
-# the default is not to use systemd for cgroups because the delegate issues still
-# exists and systemd currently does not support the cgroup feature set required
-# for containers run by docker
-ExecStart=/usr/bin/dockerd
-ExecReload=/bin/kill -s HUP $MAINPID
-# Having non-zero Limit*s causes performance problems due to accounting overhead
-# in the kernel. We recommend using cgroups to do container-local accounting.
-LimitNOFILE=infinity
-LimitNPROC=infinity
-LimitCORE=infinity
-# Uncomment TasksMax if your systemd version supports it.
-# Only systemd 226 and above support this version.
-#TasksMax=infinity
-TimeoutStartSec=0
-# set delegate yes so that systemd does not reset the cgroups of docker containers
-Delegate=yes
-# kill only the docker process, not all processes in the cgroup
-KillMode=process
-# restart the docker process if it exits prematurely
-Restart=on-failure
-StartLimitBurst=3
-StartLimitInterval=60s
-
-[Install]
-WantedBy=multi-user.target