Only run pre-mount hook zfs-load-key on systemd

Reviewed-by: Kash Pande <kash@tripleback.net>
Reviewed-by: bunder2015 <omfgbunder@gmail.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Matthew Thode <mthode@mthode.org>
Closes openzfs#7136
Closes openzfs#7140

contrib/dracut/90zfs/zfs-load-key.sh.in

@@ -1,5 +1,8 @@
 #!/bin/bash
 
+# only run this on systemd systems, we handle the decrypt in mount-zfs.sh in the mount hook otherwise
+[[ -e /bin/systemctl ]] || return 0
+
 # This script only gets executed on systemd systems, see mount-zfs.sh for non-systemd systems
 
 # import the libs now that we know the pool imported