Camera : Fix the issue of overlay having to refer to de-allocated buffers.

Both before and after the postview is displayed when the snapshot is taken,there is a possiblity of the
display referring to de-allocated preview or display buffer.So making an offline copy in first case
and delaying de-allocation in the second case so as to always queue a new buffer and de-allocate the old one.

CRs-Fixed : 254637

Change-Id: I970ed2311bb87721cafaf2e4e1d03876bc32784a
2 files changed