Switch btrfs-* services to Type=exec

[karlmistelberger]

Type=simple causes trouble with After=... ordering of systemd services. Type=exec will repair ordering issue.

[lkraav]

Type=simple causes trouble with After=... ordering of systemd services. Type=exec will repair ordering issue.

What's the trouble?

[karlmistelberger]

The behaviour is explained here: https://unix.stackexchange.com/questions/705839/systemd-firewall-service-unit-type-exec-or-type-oneshot

Mutually exclusive services will collide when declared simple. The will chain if declared exec or oneshot:

6700k:~ # grep -r =oneshot /etc/
/etc/systemd/system/dup.service:Type=oneshot
/etc/systemd/system/btrbk.service:Type=oneshot
/etc/systemd/system/btrfs-scrub.service.d/override.conf:Type=oneshot
/etc/systemd/system/btrfs-balance.service.d/override.conf:Type=oneshot
6700k:~ #