Description

As reported in issue #285, running postlock in a subshell and immediately returning from lockselect() has a high chance of hitting exit 0 before xset and dunstctl get a chance to execute.

Run both prelock and postlock synchronously within lockselect().

Fixes #285

How Has This Been Tested?

Running with set -x shows both xset and dunstctl executing reliably as expected, and xset q shows the original DPMS standby time after a succesful unlock.

Checklist:

• I have performed a self-review of my own code/checked that ShellCheck succeeds
  There are 2 existing errors unrelated to my changes:

In betterlockscreen line 610:
        local position="${geometry#*${cols[1]}}"
                                    ^--------^ SC2295 (info): Expansions inside ${..} need to be quoted separately, otherwise they match as patterns.

In betterlockscreen line 611:
        local resolution="${geometry%${position}*}"
                                     ^---------^ SC2295 (info): Expansions inside ${..} need to be quoted separately, otherwise they match as patterns.

• I have made corresponding changes to the documentation (if applicable)