systemd: fix broken links for sysvinit-compatible commands

systemd: fix broken links for sysvinit-compatible commands

Since commit[1], PACKAGECONFIG[sysvinit] is not enabled by default when
sysvinit is not in DISTRO_FEATURES, which causes the following
sysvinit-compatible commands/services to not be built and installed:

  runlevel
  telinit
  rc-local.service
  systemd-initctl
  systemd-initctl.service
  systemd-rc-local-generator
  systemd-sysv-generator
  systemd-update-utmp-runlevel.service

Therefore, links to these commands/services should only be created when
PACKAGECONFIG[sysvinit] is enabled.

[1] https://git.openembedded.org/openembedded-core/commit/?id=3668235fd60a9027608f37251c4b453ed21b3687

Signed-off-by: Yi Zhao <yi.zhao@windriver.com>
Signed-off-by: Mathieu Dubois-Briand <mathieu.dubois-briand@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
(cherry picked from commit a20b698f1acdee972cf1ff570b09a2e2c36bef1a)
Signed-off-by: Steve Sakoman <steve@sakoman.com>