contrib: systemd: set Limit* to infinity

There is a not-insignificant performance overhead for all containers (if
containerd is a child of Docker, which is the current setup) if systemd
sets rlimits on the main Docker daemon process (because the limits
propogate to all children).

Signed-off-by: Aleksa Sarai <asarai@suse.de>

contrib/init/systemd/docker.service

@@ -11,8 +11,10 @@ Type=notify
 # for containers run by docker
 ExecStart=/usr/bin/dockerd -H fd://
 ExecReload=/bin/kill -s HUP $MAINPID
-LimitNOFILE=1048576
-LimitNPROC=1048576
+# 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.