Refactor ITs to use `LedgerSpecifier.VALIDATED` so that Clio returns the correct result

[sappenin]

This gist highlights some occasionally failed CI builds that only fail on Clio. After consulting with the Clio engineering team, the following hypothesis resulted:

...if you are specifying `current` you should technically be getting the response from rippled. I can imagine this was 
deliberately setup this way because Clio might not have ingested the ledger that you mint the NFT in just yet. What
 could maybe happen is that Clio forwards the request through one of the connections to its ETL source (p2p) nodes. 
And maybe the one we ask for the NFT does not yet know about it somehow?

To resolve the occasinoally failing Clio build, we should make the default LedgerSpecifier in any IT request builder to be LedgerSpecifier.VALIDATED instead of LedgerSpecifier.CURRENT, and see if this build failure still happens. In particular, this line of code is likely a culprit if the above hypothesis is correct.