test: update test-run

Support 'use_unix_sockets_iproto' suite.ini option in 'core = app' test
suites. It'll allow to workaround TCP port choosing race (see more in
[1]) by using Unix sockets instead of TCP ones: we did the same for
'core = tarantool' test suites in [2].

[1]: https://github.com/tarantool/test-run/issues/141
[2]: 60f84cbf ('test: use unix sockets
     for iproto connections')

Part of #4459.