detect VTY TELNET port connection failures in TTCN3 tests

Pass the CTRL_DETECT_CONNECTION_ESTABLISHMENT_RESULT parameter to
the TELNET port by default. This allows tests to make progress
into an error handling path if they are started while the osmo-*
program they want to connect on VTY is not running.

Observed with osmo-ggsn tests, where if the one test runs
into a VTY connection failure the subsequent test would get
stuck forever in a map() call on the VTY TELNET port.

Change-Id: I9acf7793d5d68aec6d087cff254a10d8b673dab1
Related: OS#3149
diff --git a/bts/BTS_Tests.default b/bts/BTS_Tests.default
index 502c17f..f254993 100644
--- a/bts/BTS_Tests.default
+++ b/bts/BTS_Tests.default
@@ -12,6 +12,7 @@
 *.BTSVTY.CTRL_DETECT_SERVER_DISCONNECTED := "yes"
 *.BTSVTY.CTRL_READMODE := "buffered"
 *.BTSVTY.CTRL_CLIENT_CLEANUP_LINEFEED := "yes"
+*.BTSVTY.CTRL_DETECT_CONNECTION_ESTABLISHMENT_RESULT := "yes"
 *.BTSVTY.PROMPT1 := "OsmoBTS> "
 *.PCU.socket_type := "SEQPACKET"