net: Break disconnecting out of Ban()

These are separate events which need to be carried out by separate subsystems.

This also cleans up some whitespace and tabs in qt to avoid getting flagged by
the linter.

Current behavior is preserved.

src/interfaces/node.h

@@ -113,7 +113,10 @@ public:
     //! Unban node.
     virtual bool unban(const CSubNet& ip) = 0;
 
-    //! Disconnect node.
+    //! Disconnect node by address.
+    virtual bool disconnect(const CNetAddr& net_addr) = 0;
+
+    //! Disconnect node by id.
     virtual bool disconnect(NodeId id) = 0;
 
     //! Get total bytes recv.