When adding a new source, the spinner starts spinning before a connection/change is made

[Sebastiaan127001]

Describe the bug
When adding a new source, the spinner starts spinning before a connection/change is made

To Reproduce
Steps to reproduce the behaviour:

1. create metric Security Warnings
2. Add new source ZAP
3. See spinner start spinning before any change is made
4. See error

Expected behaviour
Wait until toaster says: Connection OK

Screenshots

[fniessink]

Note the popup is also incorrect:

"Latest measurement out of date
The source configuration of this metric was changed after the latest measurement."

This should say that there is no measurement yet due to incomplete configuration:

"No measurement available yet
Please configure the source to allow for collection measurement data."