Fixed Coverity reported issue.
Fixed Coverity reported issue.

CID 11838: Uninitialized scalar field (UNINIT_CTOR)
Non-static class member _alphaFuncKey is not initialized in this constructor nor in any functions that it calls.
Non-static class member _cyleBackwardKey is not initialized in this constructor nor in any functions that it calls.
Non-static class member _cyleForwardKey is not initialized in this constructor nor in any functions that it calls.
Non-static class member _sampleDensityKey is not initialized in this constructor nor in any functions that it calls.
Non-static class member _transparencyKey is not initialized in this constructor nor in any functions that it calls.
Non-static class member _updateAlphaCutOff is not initialized in this constructor nor in any functions that it calls.
Non-static class member _updateSampleDensity is not initialized in this constructor nor in any functions that it calls.
Non-static class member _updateTransparency is not initialized in this constructor nor in any functions that it calls.



jtorresfabra/osg,artoolkit/osg,tomasthoresen/osg,scrawl/osg,artoolkit/osg,tomasthoresen/osg,marchelbling/osg,tomasthoresen/osg,scrawl/osg,jtorresfabra/osg,openscenegraph/osg,marchelbling/osg,marchelbling/osg,marchelbling/osg,scrawl/osg,openscenegraph/osg,jtorresfabra/osg,openscenegraph/osg,tomasthoresen/osg,openscenegraph/osg,scrawl/osg,artoolkit/osg,jtorresfabra/osg,artoolkit/osg