Alter if condition when create API is called

What does this MR do?

When the toggle button to create the self monitoring project is clicked, sometimes there are multiple calls to the create API.

This MR prevents the self_monitoring create API from being called by the watcher when the component is in the loading state or when the self_monitoring_project already exists.

This feature is currently behind a feature flag, which is why I've not added a changelog entry.

Screenshots

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers
• Informed Infrastructure department of a default or new setting change, if applicable per definition of done

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• Label as security and @ mention @gitlab-com/gl-security/appsec
• The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• Security reports checked/validated by a reviewer from the AppSec team