Changes made to installhelper and make_munki_pkg.sh (#1216)

* Update installhelper

• Amended the user bootout and bootstrap commands to not be ran via `launchctl asuser`

* Update MainMenu.xib

• Centered the MunkiStatus.app window icon
• Changed the icon from AppIcon to NSApplicationIcon (which then allows for changing the icon via NSWorkspace's setIcon)

* Corrections to installhelper

* Update installhelper

---------

Co-authored-by: Greg Neagle <Gregneagle@mac.com>

code/tools/pkgresources/Scripts_launchd/postinstall

@@ -12,7 +12,7 @@ then
     if [ -f  "${installHelper}" ]
     then
         /bin/echo "Loading ${installHelper}..."
-        "${installHelper}" launchd &
+        "${installHelper}" launchd
     else
         /bin/echo "Cannot locate: ${installHelper}..."
     fi