Incorrect stereo flag calculation

[Svetlana-Asinovskaia]

Tested on Ketcher v2.2.1-140-gcbb822cf

Scenario 1.
Steps to reproduce:

1. Launch Ketcher.
2. Create a structure (e.g. chain).
3. Add two stereobonds to one of the atoms (e.g. Single Up bonds).
4. Click the 'Undo' button.

Expected result: Stereo flag is present on the canvas as the structure has one stereocenter marked with one stereobond.
Actual result: Stereo flag disappears after the "Undo" action.

Scenario 2.
Steps to reproduce:

1. Launch Ketcher.
2. Create a structure (e.g. chain).
3. Add a stereobond to one of the atoms (e.g. Single Up bond).
4. Change any other bond with Double cis/trans bond (it is reproduced with all types of bonds except the stereo ones).
5. Click the 'Undo' button.
6. Click the 'Undo' button again.
7. Click the 'Redo' button.

Expected result: The stereo flag remains without changes (is not changed from ABS(Chiral) to Mixed). After the "Redo" action the stereo flag is present on the canvas.
Actual result: The stereo flag is changed into Mixed. It is returned to the canvas with the double cis/trans bond.

[Svetlana-Asinovskaia]

Release/2.3 The issue is closed as fixed.