tests: fix running env variables

After updating tarantool sdk version to the 3.2.0 stopping instance in
`test_running_env_variables` causes an error with cleaning all logs in
json format that was written before. So it wasn't possible to determine
json format after stopping instance.

After the patch the order of distructing tarantool was moved to the
special `finally` block. Determination of json format was also updated
with `wait_string_in_file` function with special timeout.

Part of #931

test/integration/running/test_running.py

@@ -14,7 +14,7 @@
                    initial_xlog, kill_child_process, lib_path, log_file,
                    log_path, pid_file, run_command_and_get_output, run_path,
                    wait_file, wait_for_lines_in_output, wait_instance_start,
-                   wait_instance_stop)
+                   wait_instance_stop, wait_string_in_file)
 
 
 def test_running_base_functionality(tt_cmd, tmpdir_with_cfg):
@@ -578,51 +578,48 @@ def test_running_env_variables(tt_cmd, tmpdir_with_cfg):
     # Copy the test application to the "run" directory.
     test_app_path = os.path.join(os.path.dirname(__file__), "test_env_app", "test_env_app.lua")
     shutil.copy(test_app_path, tmpdir)
+
     # Set environmental variable which changes log format to json.
     my_env = os.environ.copy()
     my_env["TT_LOG_FORMAT"] = "json"
-    # Start an instance with custom env.
-    start_cmd = [tt_cmd, "start", "test_env_app"]
-    instance_process = subprocess.Popen(
-        start_cmd,
-        cwd=tmpdir,
-        stderr=subprocess.STDOUT,
-        stdout=subprocess.PIPE,
-        text=True,
-        env=my_env
-    )
-    start_output = instance_process.stdout.readline()
-    assert re.search(r"Starting an instance", start_output)
 
-    # Check status.
-    file = wait_file(os.path.join(tmpdir, "test_env_app", run_path, "test_env_app"), pid_file, [])
-    assert file != ""
-    status_cmd = [tt_cmd, "status", "test_env_app"]
-    status_rc, status_out = run_command_and_get_output(status_cmd, cwd=tmpdir)
-    assert status_rc == 0
-    status_out = extract_status(status_out)
-    assert status_out["test_env_app"]["STATUS"] == "RUNNING"
-
-    # Stop the Instance.
-    stop_cmd = [tt_cmd, "stop", "-y", "test_env_app"]
-    stop_rc, stop_out = run_command_and_get_output(stop_cmd, cwd=tmpdir)
-    assert stop_rc == 0
-    assert re.search(r"The Instance test_env_app \(PID = \d+\) has been terminated.", stop_out)
+    try:
+        # Start an instance with custom env.
+        start_cmd = [tt_cmd, "start", "test_env_app"]
+        instance_process = subprocess.Popen(
+            start_cmd,
+            cwd=tmpdir,
+            stderr=subprocess.STDOUT,
+            stdout=subprocess.PIPE,
+            text=True,
+            env=my_env
+        )
+        start_output = instance_process.stdout.readline()
+        assert re.search(r"Starting an instance", start_output)
 
-    # Check that the process was terminated correctly.
-    instance_process_rc = instance_process.wait(1)
-    assert instance_process_rc == 0
+        # Check status.
+        file = wait_file(os.path.join(tmpdir, "test_env_app", run_path, "test_env_app"),
+                         pid_file, [])
+        assert file != ""
+        status_cmd = [tt_cmd, "status", "test_env_app"]
+        status_rc, status_out = run_command_and_get_output(status_cmd, cwd=tmpdir)
+        assert status_rc == 0
+        status_out = extract_status(status_out)
+        assert status_out["test_env_app"]["STATUS"] == "RUNNING"
 
-    # Check that log format is in json.
-    isJson = False
-    logPath = os.path.join(tmpdir, "test_env_app", "var", "log", "test_env_app", log_file)
-    with open(logPath, "r") as file:
-        for _, line in enumerate(file, start=1):
-            if "{" in line:
-                isJson = True
-                break
+        # Check that log format is in json.
+        logPath = os.path.join(tmpdir, "test_env_app", "var", "log", "test_env_app", log_file)
+        wait_string_in_file(logPath, "{")
+    finally:
+        # Stop the Instance.
+        stop_cmd = [tt_cmd, "stop", "-y", "test_env_app"]
+        stop_rc, stop_out = run_command_and_get_output(stop_cmd, cwd=tmpdir)
+        assert stop_rc == 0
+        assert re.search(r"The Instance test_env_app \(PID = \d+\) has been terminated.", stop_out)
 
-    assert isJson
+        # Check that the process was terminated correctly.
+        instance_process_rc = instance_process.wait(1)
+        assert instance_process_rc == 0
 
 
 def test_running_tarantoolctl_layout(tt_cmd, tmp_path):