Fixed bug: canvas is busy (at least one reproducing way)

[bsekachev]

Motivation and context

Resolved #3711
Resolved #3652 (related issue)

How has this been tested?

Checklist

• I submit my changes into the develop branch
• I have added a description of my changes into CHANGELOG file
• I have updated the documentation accordingly
• I have added tests to cover my changes
• I have linked related issues (read github docs)
• I have increased versions of npm packages if it is necessary (cvat-canvas,
  cvat-core, cvat-data and cvat-ui)

License

• I submit my code changes under the same MIT License that covers the project.
  Feel free to contact the maintainers if that's a concern.
• I have updated the license header for each file (see an example below)

# Copyright (C) 2021 Intel Corporation
#
# SPDX-License-Identifier: MIT

[bsekachev]

@ActiveChooN
Could you please look at the PR?

[bsekachev]

@dvkruchinin

Could you please add a test according to the scenario?

1. Activate an object
2. Start dragging it (do not release mouse)
3. Delete it using Del key
4. Try to activate another object (before fix objects can't be activated)

[dvkruchinin]

@dvkruchinin

Could you please add a test according to the scenario?

@bsekachev
Sure. I`ll update a test.