contrib: rc.archlinux.asterisk uses invalid redirect.

contrib: rc.archlinux.asterisk uses invalid redirect.

`rc.archlinux.asterisk`, which explicitly requests bash in its
shebang, uses the following command syntax:

  ${DAEMON} -rx "core stop now" > /dev/null 2&>1

The intent of which is to execute:

  ${DAEMON} -rx "core stop now"

While sending both stdout and stderr to `/dev/null`. Unfortunately,
because the `&` is in the wrong place, bash is interpreting the `2` as
just an additional argument to the `$DAEMON` command and not as a file
descriptor and proceeds to use the bashism `&>` to send stderr and
stdout to a file named `1`.

So we clean it up and just use bash's shortcut syntax.

Issue raised and a fix suggested (but not used) by peutch on GitHub¹.

ASTERISK-30449 #close

1. https://github.com/asterisk/asterisk/pull/31

Change-Id: Ie279bf4efb4d95cbf507313483d316e977303d19