Use same default for all places StartDragTime is loaded
On startup we call:
m_hints[QPlatformTheme::StartDragTime] = readConfigValue(cg, QStringLiteral("StartDragTime"), 500);
on reload we call int startDragTime = cg.readEntry("StartDragTime", 10);
if the startup time isn't set, then if a reload is triggered then it is reset to a bogus value.
Long term this clearly needs porting to KConfigXT