Do not write to wallet during LoadWallet

When debugging another issue, I found a hang-during-startup race condition due to
LoadWallet calling SetMinVersion (via LoadCryptedKey).

Writing to the file that you're in the process of reading is a bad idea.

src/wallet.cpp

@@ -71,6 +71,11 @@ bool CWallet::AddCryptedKey(const CPubKey &vchPubKey, const vector<unsigned char
     return false;
 }
 
+bool CWallet::LoadCryptedKey(const CPubKey &vchPubKey, const std::vector<unsigned char> &vchCryptedSecret)
+{
+    return CCryptoKeyStore::AddCryptedKey(vchPubKey, vchCryptedSecret);
+}
+
 bool CWallet::AddCScript(const CScript& redeemScript)
 {
     if (!CCryptoKeyStore::AddCScript(redeemScript))