CaloTPCnv: Fix roundtrip issue with CaloClusterCellLinkContainer.

When we save instances of CaloClusterCellLinkContainer, weights that are exactly one are suppressed. However, the container holds the weights as double-precision, while what we save is single-precision. So it's possible if a weight is very close to 1.0 but not exactly equal to it, it gets saved as exactly 1.0 in single-precision. So if we read and rewrite, the persistent form will change. Avoid this by converting the weight to single-precision before comparing to 1.0. See ATLASRECTS-7129.