Do not load plugin from the $PWD

I see no reason why this would make sense to look for plugins in the current
directory. And when there are plugins there, it may actually be wrong

Change-Id: I5f5aa168021fedddafce90effde0d5762cd0c4c5
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
(cherry picked from commit bf131e8d2181b3404f5293546ed390999f760404)
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>

src/corelib/plugin/qpluginloader.cpp

@@ -305,7 +305,6 @@ static QString locatePlugin(const QString& fileName)
         paths.append(fileName.left(slash)); // don't include the '/'
     } else {
         paths = QCoreApplication::libraryPaths();
-        paths.prepend(QStringLiteral(".")); // search in current dir first
     }
 
     for (const QString &path : qAsConst(paths)) {