Apparently when btrfsmaintenance package is installed, the number of PID1
reloading increases from 0 to 4.

Reloading PID1 is a quite expensive operation therefore it would be nice if
this number could be reduced at its minimum and thus helping improving the boot
process.

Please note that enabling or disabling a unit implies a reload of PID1. If a
batch of units needs to be enabled/disabled, it would be better to reload PID1
only at the end of the whole operation (see systemctl "--no-reload" option).

For the context: this has been noticed in bnc#1137373, where the batch of PID1
reloading triggered by btrfsmaintenance makes a systemd race easier to happen.