Add an option to the select Greeting: none (#6356)

* Update play_greeting.lua

* Update voicemail_edit.php

app/scripts/resources/scripts/app/voicemail/resources/functions/play_greeting.lua

@@ -47,6 +47,11 @@
 					dtmf_digits = '';
 					if (string.len(greeting_id) > 0 and greeting_id ~= "default") then
 
+						--greeting set to none, return without a greeting
+							if (greeting_id == "0") then
+								return true;
+							end
+
 						--sleep
 							session:execute("playback","silence_stream://200");