do not check VP fusion during GPS startup

[copterspace]

This is solution for #11864

[julianoes]

@mhkabir or @TSC21 can you check this?

[copterspace]

Dear colleagues, here's video example of my test flying mission: https://www.youtube.com/watch?v=RNG2Y_IHx6Y
Without #11865 it would not work.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. Thank you for your contributions.

[TSC21]

My question here is: if you have GPS and vision valid, who's going to be the one initializing the global origin? GPS or Vision? Answer: I assure it will always be GPS, cause GPS is the first sensor source to be initialized in LPE. Basically you are saying that LPE will always set the global origin from the GPS data and then use vision as odometry. Generally speaking, this is fine, as GPS is a global reference frame with no drift, while vision has an arbitrary navigation frame and tends to drift.
The logic should also work if you start with vision valid and then connect valid GPS readings, where Vision had already set the global origin.
So, I am approving and merging.