AudioAttributes: fix setInternalLegacyStreamType()

Make sure that the content type is always properly set from
legacy stream type in the case where the product strategy matching
this legacy stream type does not specify it.

Bug: 129506383
Test: playback with Youtube and check content type with audio service
dumpsys

Change-Id: Ibaac0edc21bc44a56c632fb420b94deee710869d