dracut: 90zfs: respect zfs_force=1 on systemd systems

On systemd systems provide an environment generator in order
to respect the zfs_force=1 kernel command line option.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Tony Nguyen <tony.nguyen@delphix.com>
Signed-off-by: Ahelenia Ziemiańska <nabijaczleweli@nabijaczleweli.xyz>
Closes #11403
Closes #12195

contrib/dracut/90zfs/.gitignore

@@ -1,11 +1,2 @@
-export-zfs.sh
-module-setup.sh
-mount-zfs.sh
-parse-zfs.sh
-zfs-generator.sh
-zfs-lib.sh
-zfs-load-key.sh
-zfs-needshutdown.sh
-zfs-env-bootfs.service
-zfs-snapshot-bootfs.service
-zfs-rollback-bootfs.service
+*.sh
+*.service