example: Add scenarios to select BTS for a specific band

Change-Id: Id830536c9337151818901cb25c3a568a77cdbf5e
diff --git a/example/scenarios/band-1900.conf b/example/scenarios/band-1900.conf
new file mode 100644
index 0000000..ef648ef
--- /dev/null
+++ b/example/scenarios/band-1900.conf
@@ -0,0 +1,3 @@
+resources:
+  bts:
+  - band: GSM-1900