Fix load level for UE editor

[talha-opteran]

Fixes: #4551
Fixes: #4601

About

Current method to load level may work for a packaged binary but does not work in the UE editor where it will infinitely load the requested level. This PR adds a check to make sure the current level is not reloaded.

How Has This Been Tested?

1. Load project in editor.
2. Add a "Default Environment" value in settings.json
3. Launch AirSim.
4. Before fix, editor freezes due to infinitely reloading requested level. After fix, new level is loaded.

Screenshots (if appropriate):

[ghost]

All CLA requirements met.

[jonyMarino]

Hi @talha-opteran ! Thanks for the contribution. I didn't debug your code, but I got the same behavior when trying to load the default environment

[talha-opteran]

Added fix for #4601 as well as it is related

[jonyMarino]

It seems that your PR is failing the clang-format check. Please follow these steps to resolve this:

1. check out your pull request

2. run git checkout master .clang-format in your repo's root folder

3. if you don't have npm installed, download it from https://www.npmjs.com/get-npm

4. run npm install -g clang-format

5. run clang-format -i path/to/file for each failing file (failing files can be found in the details for the clang-format check)

6. run git add -u to track all style changes

7. run git commit -am "apply style from clang-format"

8. run git merge master

9. resolve other non-style conflicts if you have any

10. push changes

Thanks for contributing to AirSim!

[jonyMarino]

Thanks!