[Regression] QML disk cache and url interception don't play nice together

qmlc files are not being properly used when url interception is active. To reproduce, run the tst_qqmlfileselector autotest with the qt.qml.diskcache logging category enabled. Each run will produce output like the following:

QDEBUG : tst_qqmlfileselector::basicTest() qt.qml.diskcache: Error loading <fileName> from disk cache: "QML source file has moved to a different location."