Revert "Use "systemctl stop --no-block" to stop netctl-auto-ng."

This reverts commit abc98dc9e0228b2c6d7c9b6d699a3b55974cda69.
"--no-block" causes problems with suspend.
Revert back to using pkill instead of systemd's killing subsystem to kill wpa_actiond.

Partially revert "Improve stop() function and make dhcpcd exit
properly."
This reverts commit dcff483031b709fcd3e1f6eb7f6f42cea36e3dc4.

wpa_actiond exits 3-5 seconds after giving it SIGTERM, and systemd waits
for all processes to exit before finishing the unit's stop job.
Such delays are unacceptable, and an attempt to use "--no-block"
fails to work with suspend (service is restarted by sleep hook before it
is completely stopped).
Kill wpa_actiond before wpa_supplicant.

Upon reading the actiond source, I've found that this is the right way.
Fix a formatting bug in man page.