Fix Colab authentication bug

[giswqs]

This PR fixes the Colab authentication bug that causes duplicate authentication. If a session has already been authenticated and initialized by EE, geemap should skip the authentication.

import ee
import geemap

ee.Authenticate()
ee.Initialize(project="YOUR-PROJECT-ID")
m = geemap.Map()

[naschmitz]

We're early-returning out of this function. We need to set the user agent at the top of the function instead of at the end.

[giswqs]

@naschmitz Does ee.data.setUserAgent(user_agent) work before authentication and initialization? If yes, we can move it to the top.

[github-actions]

🚀 Deployed on https://66981650e1b55476e24791de--opengeos.netlify.app

[giswqs]

Tested on Colab. Setting user agent does not seems to required authentication.