add handover_2G suite, with handover.py test

Via VTY, handover two lchans of a voice call from bts0 to bts1 and back.

New scenarios/bts1-* allow selecting various types for bts1,
complementing the already existing files for selecting bts0.

Change-Id: I0b2671304165a1aaae2b386af46fbd8b098e3bd8
diff --git a/sysmocom/scenarios/bts1-octphy.conf b/sysmocom/scenarios/bts1-octphy.conf
new file mode 100644
index 0000000..2eb51d1
--- /dev/null
+++ b/sysmocom/scenarios/bts1-octphy.conf
@@ -0,0 +1,4 @@
+resources:
+  bts:
+  - {}
+  - type: osmo-bts-octphy