Install sample cfg file to /etc/osmocom

Change-Id: I080ae6a4c4f92dd8df055efd25e308f8a3377d34
diff --git a/debian/osmo-bsc-mgcp.install b/debian/osmo-bsc-mgcp.install
index 828fb31..8f9b74f 100644
--- a/debian/osmo-bsc-mgcp.install
+++ b/debian/osmo-bsc-mgcp.install
@@ -1,2 +1,3 @@
+etc/osmocom/osmo-bsc-mgcp.cfg
 lib/systemd/system/osmo-bsc-mgcp.service
 usr/bin/osmo-bsc_mgcp