Noticed `getblockchaininfo` would return a `verificationprogress` > 1, especially while generating. This caps the verification progress to `1`.

Tried to append a check to functional tests but this would pass even without the patch, so it seems better to not add a superfluous check (but this can easily be reproduced by trying to generate blocks in the background and `watch`ing `getblockchainfo`).

ninja all check check-functional