dropbear: init: replace backticks with $()

This replaces deprecated backticks by more versatile $(...) syntax.

Signed-off-by: Rui Salvaterra <rsalvaterra@gmail.com>
[add commit description]
Signed-off-by: Adrian Schmutzler <freifunk@adrianschmutzler.de>

package/network/services/dropbear/files/dropbear.init

@@ -238,7 +238,7 @@ killclients()
 	while [ "${pid}" -ne 0 ]
 	 do
 		# get parent process id
-		pid=`cut -d ' ' -f 4 "/proc/${pid}/stat"`
+		pid=$(cut -d ' ' -f 4 "/proc/${pid}/stat")
 		[ "${pid}" -eq 0 ] && break
 
 		# check if client connection
@@ -249,14 +249,14 @@ killclients()
 	done
 
 	# get all server pids that should be ignored
-	for server in `cat /var/run/${NAME}.*.pid`
+	for server in $(cat /var/run/${NAME}.*.pid)
 	 do
 		append ignore "${server}"
 	done
 
 	# get all running pids and kill client connections
 	local skip
-	for pid in `pidof "${NAME}"`
+	for pid in $(pidof "${NAME}")
 	 do
 		# check if correct program, otherwise process next pid
 		grep -F -q -e "${PROG}" "/proc/${pid}/cmdline" || {