Remove reaper from containerd daemon

This allows other packages and plugins to easily exec things without
racing with the reaper.

The reaper is mostly needed in the shim but can be removed in containerd
in favor of the `exec.Cmd` apis

Signed-off-by: Michael Crosby <crosbymichael@gmail.com>

server/server_linux.go

@@ -12,12 +12,6 @@ import (
 
 // apply sets config settings on the server process
 func apply(ctx context.Context, config *Config) error {
-	if !config.NoSubreaper {
-		log.G(ctx).Info("setting subreaper...")
-		if err := sys.SetSubreaper(1); err != nil {
-			return err
-		}
-	}
 	if config.OOMScore != 0 {
 		log.G(ctx).Debugf("changing OOM score to %d", config.OOMScore)
 		if err := sys.SetOOMScore(os.Getpid(), config.OOMScore); err != nil {