base-files: coreutil-date breaks setting kernel timezone

"coreutil-date" package from the packages feed replaces the Busybox date
applet by symlinking /usr/bin/gnu-date to /bin/date. This prevents the system
init script from setting kernel timezone because the GNU date utility does not
provide such functionality:

   root@OpenWrt:~# date -k
   date: invalid option -- 'k'
   Try 'date --help' for more information.

A specific reference to the Busybox date applet prevents alternative date
utilities from breaking the system init script.

Signed-off-by: Val Kulkov <val.kulkov@gmail.com>

package/base-files/files/etc/init.d/system

@@ -27,7 +27,7 @@ system_config() {
 		ln -sf "/usr/share/zoneinfo/$zonename" /tmp/localtime && rm -f /tmp/TZ
 
 	# apply timezone to kernel
-	date -k
+	busybox date -k
 }
 
 reload_service() {