Add channel_allocator cfg attr to bts resources

Change-Id: I682809d4aeb91a36e3a35fc481e8d40d0b084fa0
diff --git a/example/defaults.conf b/example/defaults.conf
index f7bd1b1..73188d5 100644
--- a/example/defaults.conf
+++ b/example/defaults.conf
@@ -28,6 +28,7 @@
   base_station_id_code: 63
   stream_id: 255
   osmobsc_bts_type: sysmobts
+  channel_allocator: ascending
   num_trx: 1
   max_trx: 1
   trx_list: