Allow wallet files not in -walletdir directory

Remove restriction that -wallet filenames can only refer to files in the
-walletdir directory.

src/wallet/db.cpp

@@ -122,6 +122,7 @@ bool CDBEnv::Open(bool retry)
     boost::this_thread::interruption_point();
 
     fs::path pathIn = strPath;
+    TryCreateDirectories(pathIn);
     if (!LockDirectory(pathIn, ".walletlock")) {
         LogPrintf("Cannot obtain a lock on wallet directory %s. Another instance of bitcoin may be using it.\n", strPath);
         return false;