Validation timing fixes:

* Log whether consensus built a ledger we already had or were acquiring
* Don't trigger an acquire for a validation for a ledger we might be building
* When we finish building a ledger, try to accept that ledger
* If we cannot accept a built ledger, check held validations
* Correctly set isCurrent for untrusted validations
* Add appropriate logging

This fixes a race condition that could cause spurious and expensive
ledger fetches across the network and delayed recognition of
fully-validated ledger.

src/ripple_app/misc/NetworkOPs.cpp

@@ -502,7 +502,7 @@ private:
     SubMapType                                          mSubTransactions;       // all accepted transactions
     SubMapType                                          mSubRTTransactions;     // all proposed and accepted transactions
 
-    TaggedCache< uint256, Blob>                     mFetchPack;
+    TaggedCache< uint256, Blob>                         mFetchPack;
     std::uint32_t                                       mFetchSeq;
 
     std::uint32_t                                       mLastLoadBase;