policycoreutils: sandbox: do not require selinux context

seunshare can be used on non-selinux systems.  It can also be used
without transition to a new context.  Thus we should not require that a
context be set.

Signed-off-by: Eric Paris <eparis@redhat.com>
Acked-by: Dan Walsh <dwalsh@redhat.com>
2 files changed