Consistently log CValidationState on failure

Seems providing at least minimal visibility to the failure is a good practice.

The only remaining ignored state is in LoadExternalBlockFile, where logging
would likely be spammy.

src/init.cpp

@@ -684,7 +684,7 @@ void ThreadImport(std::vector<fs::path> vImportFiles)
     // scan for better chains in the block chain database, that are not yet connected in the active best chain
     CValidationState state;
     if (!ActivateBestChain(state, chainparams)) {
-        LogPrintf("Failed to connect best block\n");
+        LogPrintf("Failed to connect best block (%s)\n", FormatStateMessage(state));
         StartShutdown();
         return;
     }