Adopt `tempesta-tech.com` in LXC container test

[RomanBelozerov]

We have our wordpress tempesta-tech.com website into LXD container (deployment), but we use docker in test suite. And also we don't use our website for tests.

For testing our website in tests:

• [ ] replace Docker to LXD container in test framework;
• [ ] rework selftests.test_docker_server;
• [ ] rework t_stress tests;
• [ ] rework t_sites tests;

[krizhanovsky]

You can deploy an LXC container with a fully operational website with only one Python script call https://github.com/tempesta-tech/tempesta-tech.com#wordpress-website-deployment . The website deployment process takes quite a while, so probably an LXC image should be prepared (and updated from time to time!) to make the test run quicker or jsut move the test to nightly jobs.

This task is required to make sure that we won't break our website if we deploy a new (current) version of master Tempesta branch, so we can test the latest version of Tempesta on real life clients

[mbabitski-t]

Due to a number of problems with plain LXC, we are planning to fully migrate our site setup to Docker (private #83), rendering this issue no longer relevant.

[krizhanovsky]

Let's just implement https://github.com/tempesta-tech/tempesta-tech.com/issues/83 firstly in our test suite and then we'll be able to easier migrate from LXD to Docker on the production website. The WordPress workload will be tested in any way.

[mbabitski-t]

• [x] migrate tempesta-tech.com from LXC to Docker (minimally working, without staging scripts)
• [x] add support for Docker Compose backend
• [x] add selftests.test_docker_compose_server
• [x] adopt tempesta-tech.com in tests.
• [ ] rework t_sites tests
• [ ] rework t_stress tests

UPD: Docker container seems to have problems with our PHP installation and site produces numerous errors. Reverting to LXC.

[krizhanovsky]

Blocked https://github.com/tempesta-tech/tempesta/issues/1980