net: make Ban/Unban/ClearBan functionality consistent

- Ban/Unban/ClearBan call uiInterface.BannedListChanged() as necessary
- Ban/Unban/ClearBan sync to disk if the operation is user-invoked
- Mark node for disconnection automatically when banning
- Lock cs_vNodes while setting disconnected
- Don't spin in a tight loop while setting disconnected

src/rpc/net.cpp

@@ -565,20 +565,12 @@ UniValue setban(const UniValue& params, bool fHelp)
             absolute = true;
 
         isSubnet ? CNode::Ban(subNet, BanReasonManuallyAdded, banTime, absolute) : CNode::Ban(netAddr, BanReasonManuallyAdded, banTime, absolute);
-
-        //disconnect possible nodes
-        while(CNode *bannedNode = (isSubnet ? FindNode(subNet) : FindNode(netAddr)))
-            bannedNode->fDisconnect = true;
     }
     else if(strCommand == "remove")
     {
         if (!( isSubnet ? CNode::Unban(subNet) : CNode::Unban(netAddr) ))
             throw JSONRPCError(RPC_MISC_ERROR, "Error: Unban failed");
     }
-
-    DumpBanlist(); //store banlist to disk
-    uiInterface.BannedListChanged();
-
     return NullUniValue;
 }
 
@@ -624,8 +616,6 @@ UniValue clearbanned(const UniValue& params, bool fHelp)
                             );
 
     CNode::ClearBanned();
-    DumpBanlist(); //store banlist to disk
-    uiInterface.BannedListChanged();
 
     return NullUniValue;
 }