With both sysvinit and systemd features enabled these postinsts may actually run
on a target without systemd, so check that systemctl is present before using it.
(From OE-Core rev: ac00e56cb9daacef17a6fdebe7b8ca1667b7e1c4)
Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>