Fix png inputs sCal flag

Due to change of behavior with libpng, where files have been updated
with a METER sCal field.

Change-Id: Ic7d8bcbda32143c31e31d0a5213f1434728df008
Merge branch 'SIMPLEITK_589_FixPNGsCalField' into release

* SIMPLEITK_589_FixPNGsCalField:
  Fix png inputs sCal flag

Change-Id: Ib4481f0885b1acb4c6eeccb2b82bf4ea4a32cb3c