For the vty tests, add osmo-sgsn-accept-all.cfg (that does not need an HLR) and
use in vty_test_runner.py, otherwise the 'show sgsn' command will reply that it
could not connect to the HLR, failing the vty test which expects empty.
Change-Id: Ie3b2013198d3e2b780a4e31c36b89b58129dcacd