STYLE: Slightly refactor ImageFileWriter::Write to simplify logic

There's no need for separate logic paths to the same function call.

Change-Id: I644c33919dd103b4697e5e9648cc30f936dba8b5
ENH: Always enable Get*FromTag methods in GDCMImageIO

The GetValueFromTag and GetLabelFromTag methods don't require a
static buffer and should be fully compatible with GDCM 2.

Both function provide a major convenience and should not be
depreciated.

The functions were deprecated by
f00506be172c9d89314695788770e264f782a6d3

Change-Id: Ide5ef2b873452473dc22bafa6986ffb821a00466
Merge topic 'gdcm-tag'

1eab6cb ENH: Always enable Get*FromTag methods in GDCMImageIO
Merge topic 'imagefilewriter-clean'

9c3fc2c STYLE: Slightly refactor ImageFileWriter::Write to simplify logic