No more fHaveGUI

No more specific handling of GUI in bitcoin core.
Replace the last usage of fHaveGUI with a fForceServer
parameter on AppInit2.

src/main.cpp

@@ -41,7 +41,6 @@ bool fReindex = false;
 bool fBenchmark = false;
 bool fTxIndex = false;
 unsigned int nCoinCacheSize = 5000;
-bool fHaveGUI = false;
 
 /** Fees smaller than this (in satoshi) are considered zero fee (for transaction creation) */
 int64 CTransaction::nMinTxFee = 10000;  // Override with -mintxfee