avoid memory leak in slave jobs

Summary:
Making ~SlaveInterface virtual, the connection created in Slave constructor is now deleted. (thanks @dfaure).
Changed to new connect syntax.

BUG: 396651

Test Plan:
The leaks of the bug report are gone.

Reviewers: dfaure, #frameworks, ngraham

Reviewed By: dfaure

Subscribers: anthonyfieroni, apol, kde-frameworks-devel

Tags: #frameworks

Differential Revision: https://phabricator.kde.org/D14253

src/core/slave.cpp

@@ -171,7 +171,7 @@ void Slave::accept()
     d->slaveconnserver->deleteLater();
     d->slaveconnserver = nullptr;
 
-    connect(d->connection, SIGNAL(readyRead()), SLOT(gotInput()));
+    connect(d->connection, &Connection::readyRead, this, &Slave::gotInput);
 }
 
 void Slave::timeout()
@@ -218,7 +218,7 @@ Slave::Slave(const QString &protocol, QObject *parent)
     Q_D(Slave);
     d->slaveconnserver->setParent(this);
     d->connection = new Connection(this);
-    connect(d->slaveconnserver, SIGNAL(newConnection()), SLOT(accept()));
+    connect(d->slaveconnserver, &ConnectionServer::newConnection, this, &Slave::accept);
 }
 
 Slave::~Slave()

src/core/slaveinterface_p.h

@@ -42,7 +42,7 @@ class KIO::SlaveInterfacePrivate
           nums(0), slave_calcs_speed(false)
     {
     }
-    ~SlaveInterfacePrivate()
+    virtual ~SlaveInterfacePrivate()
     {
         delete connection;
     }