Description of problem:
When using a custom git servername the "Import from git"-flow tries to validate the git repository and if possible make a build strategy suggestion.

If the URL doesn't contain an indicator if the git provider is one of the supported providers (at the moment GitHub, GitLab, or BitBucket) it shows a dropdown so that the user can select the git provider.

If the user selects this git provider, it ignores the given servername and fetches data from the 'official public API' instead. With this, the user doesn't have the option to use an On-Premises GitLab and BitBucket installation.

Version-Release number of selected component (if applicable):
4.8

Verified on 4.8, 4.9 and 4.10 (master branch, tested with fbbf49d71c73ab56d23180de9b4eb6ca3e40a94c)
Don't tested older versions yet

How reproducible:
Always

Steps to Reproduce:
1. Switch to developer perspective
2. Navigate to Add > Import from Git
3. Open the browser network inspector
4. Enter a Git URL like https://git.mycompany.com/
5. Switch between the Git providers, if needed change the git URL to trigger a new API call

Actual results:
- When selecting GitHub and BitBucket the network calls always go to api.github.com and api.bitbucket.org (both wrong)
- When selecting GitLab the network inspector shows an API call to git.mycompany.com (correct)

Expected results:
- For each provider the URL should change, but the actual request should always go to the given servername.

Additional info:
None