Make test run self-sufficing

[DifferentialOrange]

When I prepare test environment with

tarantool config.lua

on a new repo, it fails with

2021-11-02 12:01:16.078 [49911] main/103/config.lua xlog.c:531 !> SystemError error reading directory 'snap': No such file or directory
2021-11-02 12:01:16.078 [49911] main/103/config.lua F> can't initialize storage: error reading directory 'snap'

Since tarantool can create and remove folders with fio module, it would be convenient to solve such issues in script, not manually.

Related to #106, since test run guide or test run script should be self-sufficing too.