Introduce and use osmo-bts-trx VTY cmd max_trxd_version on sysmocell-5K

Force TRXDv0 when using sysmocell-5k as a TRX, since its implementation
(different than osmo-trx) doesn't support higher versions. Furthermore,
it will crash upon receival of SETFORMAT string. By forcing maximum TRXD
version to 0, osmo-bts-trx won't sent any SETFORMAT message since 0 is
the initial version to use.

Depends: osmo-bts.git I5eb1fdc002f9d7f4acf475356d8fc998dc8f6326
Related: OS#4006
Change-Id: Ic95c38d91dba354ae64c5edbfcea3fbbf34a7de3
diff --git a/example/resources.conf.prod b/example/resources.conf.prod
index f4e9fe4..8b498d0 100644
--- a/example/resources.conf.prod
+++ b/example/resources.conf.prod
@@ -73,6 +73,7 @@
         launch_trx: false
         clock_reference: external
         trx_ip: 10.42.42.112
+        max_trxd_version: 0
 
 - label: OCTBTS 3500
   type: osmo-bts-octphy