buttons: make all button handler scripts return 0

this is required by the new button timeout feature

Signed-off-by: John Crispin <blogic@openwrt.org>

SVN-Revision: 46471

package/base-files/files/etc/rc.button/failsafe

@@ -1,3 +1,5 @@
 #!/bin/sh
 
 [ "${TYPE}" = "switch" ] || echo ${BUTTON} > /tmp/failsafe_button
+
+return 0