Fix #flingAndSnap to check all the scroll item for offset range

Summary:
When calculating the offset range, we assume the first item is always at offset zero position and skipped that (as the smallerOffset is zero). However, this may not be the case in some situations. This diff changes the range measuring loop to always start from the first item.

Changelog:
[Android][Fixed] - Do NOT skip the first child view in the scroll view group when measuring the lower and upper bounds for snapping.

Reviewed By: mdvacca

Differential Revision: D31887086

fbshipit-source-id: af7221a621b2719d057afa6b64aa91c94ac01295