prevent race on execute_on_answer called from the B-leg of a call

src/include/switch_types.h

@@ -1096,6 +1096,7 @@ typedef enum {
 	CF_RECOVERED,
 	CF_JITTERBUFFER,
 	CF_DIALPLAN,
+	CF_BLOCK_BROADCAST_UNTIL_MEDIA,
 	/* WARNING: DO NOT ADD ANY FLAGS BELOW THIS LINE */
 	CF_FLAG_MAX
 } switch_channel_flag_t;