[BUG] Multiple datasource test connection didn't test correctly

[Flyingliuhub]

Describe the bug

The multiple datasource test connection didn't test correctly in some cases, like as "Username & Password", and serverless cases

To Reproduce
Steps to reproduce the behavior:

1. Go to 'Data source'
2. Click on 'Create data source'
3. Fill out endpoint URL "https://google.com"
4. Choose "Username & Password"
5. Fill out any Username and Password
6. Click 'Test connection'
7. It is showing up "Connecting to the endpoint using the provided authentication method was successful."

Expected behavior
It should throw error that "failed to connection"

OpenSearch Version
2.11

Dashboards Version
2.11

Plugins

N/A

Screenshots

Host/Environment (please complete the following information):

• OS: MacOS
• Browser and version: firefox 115.5.0esr

Additional context

Add any other context about the problem here.