Defer the ZSL stream by 500 ms

This forces the preview to start before the ZSL stream is
attached, and then attaches the ZSL stream to the repeating
request after a 500ms delay to give the system time to allocate
the underlying buffers for the ZSL image readers.

Bug: 19076469
Change-Id: I75ea28ead5b009e0f65f5f00c0522bcb2219cb22
7 files changed