Revert upgrade marker locking (#8938) (#8957)

* Revert "Short-circuit readMarkerFile if upgrade marker does not exist (#8463)"

This reverts commit 07e7a6b.

* Revert "Lock upgrade marker (#8254)"

This reverts commit 5b280bd.

Co-authored-by: Paolo Chilà <[email protected]>

Author: mergify[bot]