Add extra lock check for OSX build

Apparently my upstream checkpoint was in the middle of a series of
commits by ianofsky separating wallet from the main code.  This means
that I have to add this main lock which will be replaced by the
locked_chain interface in a subsequence catchup.

src/wallet/rpcwallet.cpp

@@ -5493,6 +5493,7 @@ UniValue claimpegin(const JSONRPCRequest& request)
 
     // To check if it's not double spending an existing pegin UTXO, we check mempool acceptance.
     CValidationState acceptState;
+    LockAnnotation lock(::cs_main); //TODO(stevenroose) replace with locked_chain later
     bool accepted = ::AcceptToMemoryPool(mempool, acceptState, MakeTransactionRef(mtx), nullptr /* pfMissingInputs */,
                             nullptr /* plTxnReplaced */, false /* bypass_limits */, maxTxFee, true /* test_accept */);
     if (!accepted) {

src/wallet/wallet.cpp

@@ -2510,6 +2510,7 @@ bool CWallet::SelectCoinsMinConf(const CAmountMap& mapTargetValue, const CoinEli
 
 bool CWallet::SelectCoins(const std::vector<COutput>& vAvailableCoins, const CAmountMap& mapTargetValue, std::set<CInputCoin>& setCoinsRet, CAmountMap& mapValueRet, const CCoinControl& coin_control, CoinSelectionParams& coin_selection_params, bool& bnb_used) const
 {
+    AssertLockHeld(cs_wallet); // mapWallet
     std::vector<COutput> vCoins(vAvailableCoins);
 
     // coin control -> return all selected outputs (we want all selected to go into the transaction for sure)