Mark a singleton instance as a leader manually

[Totktonada]

Otherwise 'set' and 'register' tests, which use synchronous spaces, fail
with the 'The synchronous transaction queue doesn't belong to any
instance' error.

Those tests did pass before the change 1 in tarantool, which was made
in the scope of the issue 2. The commit land into release branches as
2.7.2-160-g7310288fa, 2.8.1-168-g806123567, 2.9.0-221-g362e9a668.

Fixes #92

---

Sorry, I don't know how to run it to test the changes. It is blind
attempt to fix the problem. I would appreciate a help.

[sergepetrenko]

Although that's not needed, it's ok to call promote every time an instance starts.
You could only call promote once, during bootstrap. But there's no need to overcomplicate, so LGTM.

[Totktonada]

I didn't know that this information is persisted. It's easy to move it into box.once(), I'll do.

[Totktonada]

Verified in tarantool/tarantool CI this way:

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 8037c30a7a0..0a13c003bbb 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -200,6 +200,7 @@ if (WITH_JEPSEN)
     ExternalProject_Add(
         jepsen-tests
         GIT_REPOSITORY https://github.com/tarantool/jepsen.tarantool
+        GIT_TAG e27335ba54d512dfde7ed33a1182ad5fa48eb93c
         CONFIGURE_COMMAND ""
         BUILD_COMMAND ""
         INSTALL_COMMAND ""

The problem looks fixed.

I found another problem (occurs from time to time, hit me once) with incorrect apt source list:

openstack_compute_instance_v2.instance[0] (remote-exec): E: Type 'to' is not known on line 50 in source list /etc/apt/sources.list
openstack_compute_instance_v2.instance[0] (remote-exec): E: The list of sources could not be read.

I'll try to collect more information about it in background. It is irrelevant here.

[Totktonada]

Added information about the change in tarantool, which causes the problem here. Thanks to @sergepetrenko for pointing it out.

[ligurio]

Verified in tarantool/tarantool CI this way:

I think it is worth to add a link to successful run - https://github.com/tarantool/tarantool/actions/runs/1403828057

[ligurio]

Thanks for the fix!