Given commit 330ae3d3:

    lxccontainer: detect if we should send SIGRTMIN+3

    This is required by systemd to cleanly shutdown. Other init systems should not
    have SIGRTMIN+3 in the blocked signals set.

we should stop symlinking halt.target to sigpwr.target for systemd.
Signed-off-by: Christian Brauner <cbrauner@suse.de>