Add option to disable new session keys

This adds an `--no-new-keyring` flag to run and create so that a new
session keyring is not created for the container and the calling
processes keyring is inherited.

Fixes #818

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

utils_linux.go

@@ -171,6 +171,7 @@ func createContainer(context *cli.Context, id string, spec *specs.Spec) (libcont
 		CgroupName:       id,
 		UseSystemdCgroup: context.GlobalBool("systemd-cgroup"),
 		NoPivotRoot:      context.Bool("no-pivot"),
+		NoNewKeyring:     context.Bool("no-new-keyring"),
 		Spec:             spec,
 	})
 	if err != nil {