Update containerd systemd unit file

Synchronizes unit file with CRI's version

Signed-off-by: Derek McGowan <derek@mcg.dev>

containerd.service

@@ -11,6 +11,7 @@ Type=notify
 Delegate=yes
 KillMode=process
 Restart=always
+RestartSec=5
 # Having non-zero Limit*s causes performance problems due to accounting overhead
 # in the kernel. We recommend using cgroups to do container-local accounting.
 LimitNPROC=infinity
@@ -19,6 +20,7 @@ LimitNOFILE=1048576
 # Comment TasksMax if your systemd version does not supports it.
 # Only systemd 226 and above support this version.
 TasksMax=infinity
+OOMScoreAdjust=-999
 
 [Install]
 WantedBy=multi-user.target