WIP: Fix flaky fails with hang tests

The problem is that frontend wait infinitely for a storage server, which
have not been initialized due to the error like the following.

```
Start failed: builtin/box/console.lua:560: failed to create server
localhost:57988: Address already in use
```

The problem is described in [1] (see comment itself, the issue is about
the another problem).

The gist of the fix is using unix sockets for admin console of
non-default servers (storages). The option 'use_unix_sockets' affects
only console (admin) socket and does nothing with binary (listen) port
of a storage. It is critical in the benchmarking test suite.

TBD: update test-run from master after test-run's PR #123.

[1]: tarantool/test-run#115 (comment)

Author: Totktonada

test-run

@@ -3,6 +3,7 @@ core = app
 description = microbenchmarking
 config = suite.cfg
 is_parallel = False
+use_unix_sockets = True
 long_run =
     forking-2-100-1.test.lua
     forking-2-1-1.test.lua

test/bench/suite.ini

@@ -3,3 +3,4 @@ core = app
 description = tests different setups simultaneously
 config = suite.cfg
 is_parallel = True
+use_unix_sockets = True

test/common/suite.ini

@@ -3,3 +3,4 @@ core = app
 description = tests on features which are not related to specific executor
 is_parallel = True
 config = suite.cfg
+use_unix_sockets = True

test/extra/suite.ini

@@ -3,3 +3,4 @@ core = app
 description = tests with space accessor
 config = suite.cfg
 is_parallel = False
+use_unix_sockets = True