16c6d626fe
Currently, scylla_fstrim_setup does not start scylla-fstrim.timer and
just enables it, so the timer starts only after rebooted.
This is incorrect behavior, we start start it during the setup.
Also, unmask is unnecessary for enabling the timer.
Fixes #14249
Closes #14252
(cherry picked from commit c70a9cbffe)
Closes #14420