Variable ALTCONF ignored when service is used in Debian

When variable ALTCONF is defined, the command start prints the message
"Unable to open specified master config file '"/etc/asterisk/asteris..."
and use default configurations.

ASTERISK-28332

Change-Id: I7595e582a0ee2c1051ea35435e247e27906957ef

contrib/init.d/rc.debian.asterisk

@@ -85,7 +85,7 @@ case "$1" in
 		chgrp $AST_GROUP $ASTVARRUNDIR
 	fi
 	if [ $ALTCONF ]; then
-		ASTARGS="$ASTARGS -C \"$ALTCONF\""
+		ASTARGS="$ASTARGS -C $ALTCONF"
 	fi
 	if [ "x$COREDUMP" = "xyes" ]; then
 		ASTARGS="$ASTARGS -g"