update install files

arch/libnetctlgui.install

@@ -1,5 +1,5 @@
 post_install() {
-  xdg-icon-resource forceupdate --theme hicolor 2> /dev/null
+  true
 }
 
 post_upgrade() {

arch/netctlgui-helper.install

@@ -1,5 +1,9 @@
 post_install() {
   setcap cap_setuid=ep usr/bin/netctlgui-helper 2>/dev/null || chmod +s usr/bin/ping
+  cat << EOF
+Note: users should be in network group if you want to get them access to the system bus
+See http://arcanis.name/devs/netctl-gui-security-notes.html#helper
+EOF
 }
 
 post_upgrade() {