* anders/diameter/21.1/OTP-15202:
  vsn -> 2.1.6
  Update appup for 21.1

* anders/diameter/dpr/OTP-15198:
  Fix function_clause when sending a request after an outgoing DPA

OTP-15198  Fix function_clause when sending a request after outgoing DPA

After DPR, the intention is that outgoing answers are sent and outgoing
requests are discarded. This was the case when the DPR was outgoing, but
if it was incoming then a subsequent outgoing request resulted in a
function_clause, bringing down the diameter_peer_fsm gen_server
associated with the transport connection in question.

With diameter_tcp/sctp, the failure can result in the connection being
reset before the peer closes it in response to DPA, but is otherwise
harmless since DPR means that the connection is already on its way down.

* anders/diameter/21.0/OTP-15110:
  Make diameter_app_SUITE fail more usefully
  Simplify app-file generation
  Match in diameter_app_SUITE to identify an unexpected path
  Don't use deprecated ssl:ssl_accept/1-3
  Don't use deprecated erlang:get_stacktrace/0

The badmatch in the grandparent commit is ssl not being installed:

=== Reason: no match of right hand side value {ssl,non_existing,
                                                    ["non_existing"]}
  in function  diameter_app_SUITE:app/1 (diameter_app_SUITE.erl, line 266)
  in call from diameter_app_SUITE:'-xref/1-fun-3-'/2 (diameter_app_SUITE.erl, line 214)
  in call from lists:'-filter/2-lc$^0/1-0-'/2 (lists.erl, line 1286)
  in call from diameter_app_SUITE:xref/1 (diameter_app_SUITE.erl, line 214)
  in call from test_server:ts_tc/3 (test_server.erl, line 1545)
  in call from test_server:run_test_case_eval1/6 (test_server.erl, line 1063)
  in call from test_server:run_test_case_eval/9 (test_server.erl, line 995)

Tweak the failure a bit more, without fixing it.