BUG: ExpandRGBPalette used instead of IsReadAsScalarPlusPalette
BUG: ExpandRGBPalette used instead of IsReadAsScalarPlusPalette

In ReadGenericImage, the information about the image is alreadyextracted.
GetIsReadAsScalarPlusPalette() should therefore be used in addition of
GetExpandRGBPalette().

This commit doesn't affect the current behavior of tiff reading,
but make the logic of tiff reading more coherent
and robust to future changes.

Change-Id: I4b124e3f68471a38ddbf1731cd1f29a8922bdc59

fbudin69500/ITK,PlutoniumHeart/ITK,vfonov/ITK,LucasGandel/ITK,spinicist/ITK,stnava/ITK,stnava/ITK,BRAINSia/ITK,fbudin69500/ITK,malaterre/ITK,PlutoniumHeart/ITK,blowekamp/ITK,LucasGandel/ITK,spinicist/ITK,blowekamp/ITK,LucasGandel/ITK,InsightSoftwareConsortium/ITK,PlutoniumHeart/ITK,fbudin69500/ITK,InsightSoftwareConsortium/ITK,stnava/ITK,richardbeare/ITK,BRAINSia/ITK,blowekamp/ITK,LucasGandel/ITK,hjmjohnson/ITK,spinicist/ITK,hjmjohnson/ITK,InsightSoftwareConsortium/ITK,vfonov/ITK,thewtex/ITK,richardbeare/ITK,malaterre/ITK,spinicist/ITK,stnava/ITK,blowekamp/ITK,spinicist/ITK,thewtex/ITK,hjmjohnson/ITK,Kitware/ITK,thewtex/ITK,vfonov/ITK,BRAINSia/ITK,InsightSoftwareConsortium/ITK,fbudin69500/ITK,blowekamp/ITK,blowekamp/ITK,thewtex/ITK,BRAINSia/ITK,Kitware/ITK,BRAINSia/ITK,thewtex/ITK,vfonov/ITK,BRAINSia/ITK,fbudin69500/ITK,vfonov/ITK,Kitware/ITK,PlutoniumHeart/ITK,spinicist/ITK,LucasGandel/ITK,LucasGandel/ITK,malaterre/ITK,hjmjohnson/ITK,stnava/ITK,stnava/ITK,malaterre/ITK,hjmjohnson/ITK,malaterre/ITK,Kitware/ITK,Kitware/ITK,PlutoniumHeart/ITK,malaterre/ITK,stnava/ITK,spinicist/ITK,blowekamp/ITK,BRAINSia/ITK,richardbeare/ITK,fbudin69500/ITK,stnava/ITK,Kitware/ITK,malaterre/ITK,PlutoniumHeart/ITK,hjmjohnson/ITK,thewtex/ITK,hjmjohnson/ITK,richardbeare/ITK,blowekamp/ITK,richardbeare/ITK,vfonov/ITK,spinicist/ITK,malaterre/ITK,PlutoniumHeart/ITK,vfonov/ITK,thewtex/ITK,malaterre/ITK,LucasGandel/ITK,stnava/ITK,richardbeare/ITK,vfonov/ITK,InsightSoftwareConsortium/ITK,LucasGandel/ITK,spinicist/ITK,fbudin69500/ITK,InsightSoftwareConsortium/ITK,richardbeare/ITK,Kitware/ITK,fbudin69500/ITK,vfonov/ITK,InsightSoftwareConsortium/ITK,PlutoniumHeart/ITK