Incorrect deep merge of suites with has_children = false

[mrbinwin]

Hello!

service-api v. 5.4.0

There is a bug in merge_launch() function that leads to incorrect deep merge of suites (from different launches) that have the same name but one of them have no children (test_item.has_children = false).

test_item 1:

item_id	unique_id	name	path	has_children	parent_id	launch_id
5253296	auto:85f69a4c071c3d073d354f31bc82e6a4	Root User Story	5253296	false		261773

test_item 2:

item_id	unique_id	name	path	has_children	parent_id	launch_id
23471137	auto:85f69a4c071c3d073d354f31bc82e6a4	Root User Story	23471137	true		599388

We run a deep merge of their launches: 261773 and 599388

Actual result:

test_item after merge:

item_id	unique_id	name	path	has_children	parent_id	launch_id
31452655	auto:26204e06d9f9326dd60f05075c3fc258	Root User Story	31452655	false		638339

The result test_item.has_children = false
Also rows related to new launch and this test_item have not been inserted to statistics table.
So users are unable to see test results of this launch on UI.

It happens because this condition is false: https://github.com/reportportal/migrations/blob/develop/migrations/25_deep_merge_nested_steps_path_fix.up.sql#L70

Expected result:
If one of merging test_items has children test_items and has_children=true,
the result test_item also must have has_children=true and related statistics (total, passed, failed...) must be inserted into statistics table