bitbake-layers: close files in apply_append()

It's recommended practice to close files when finished with them and the
code in this function was not doing this.

(Bitbake rev: 470a160813ce6cf04f83258d46ded5c2ab8bc520)

Signed-off-by: Paul Eggleton <paul.eggleton@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

bitbake/bin/bitbake-layers

@@ -307,6 +307,8 @@ build results (as the layer priority order has effectively changed).
         recipefile.write('\n')
         recipefile.write('##### bbappended from %s #####\n' % self.get_append_layer(appendname))
         recipefile.writelines(appendfile.readlines())
+        recipefile.close()
+        appendfile.close()
 
     def do_show_appends(self, args):
         """list bbappend files and recipe files they apply to