test: fix flaky test_restart_simple_app_auto_yes

The patch add proper check that tarantool is started.
Also logging was improved to get more information in case of failure.

Closes TNTP-7654

Author: elhimov

test/conftest.py

@@ -273,6 +273,7 @@ def tt_app(tt, tt_path, tt_instances, tt_running_targets, tt_post_start):
         p = tt.run("start", target)
         assert p.returncode == 0
     app.running_instances = app.instances_of(*tt_running_targets)
+    assert tt_helper.wait_box_status(5, app, app.running_instances, ["running"])
     if tt_post_start is not None:
         tt_post_start(app)
     yield app

test/integration/restart/test_restart.py

@@ -109,6 +109,12 @@ def check_restart(tt, tt_app, target, input, is_confirm, *args):
     for inst in tt_app.instances:
         was_running = inst in tt_app.running_instances
         if is_confirm and inst in target_instances:
+            if status[inst]["STATUS"] != "RUNNING":
+                with open(tt_app.log_path(inst, utils.log_file)) as f:
+                    print(f"log of instance {inst} ======")
+                    print(f.read())
+                    print("=============================")
+                    assert False
             assert status[inst]["STATUS"] == "RUNNING"
             assert f"Starting an instance [{inst}]" in out
             if was_running: