Pull request: 3457 fix service reload

Merge in DNS/adguard-home from 3457-darwin-svc-reload to master

Closes #3457.

Squashed commit of the following:

commit e3d6fbccf8373194360b6480e2d702ccd0ec7107
Author: Eugene Burkov <e.burkov@adguard.com>
Date:   Wed Aug 18 00:52:39 2021 +0300

    aghos: imp docs

commit 220d37ebc1e0c2e9ba37a34650bff1480bd2fcf6
Author: Eugene Burkov <e.burkov@adguard.com>
Date:   Tue Aug 17 15:45:52 2021 +0300

    all: fix ps

internal/aghos/os_linux.go

@@ -25,10 +25,6 @@ func haveAdminRights() (bool, error) {
 	return os.Getuid() == 0, nil
 }
 
-func sendProcessSignal(pid int, sig syscall.Signal) error {
-	return syscall.Kill(pid, sig)
-}
-
 func isOpenWrt() (ok bool) {
 	var err error
 	ok, err = FileWalker(func(r io.Reader) (_ []string, cont bool, err error) {