IOMX: work against metadata buffer spoofing

IOMX: work against metadata buffer spoofing

- Prohibit direct set/getParam/Settings for extensions meant for
  OMXNodeInstance alone. This disallows enabling metadata mode
  without the knowledge of OMXNodeInstance.
- Do not share metadata mode buffers cross process.
- Disallow setting up metadata mode/tunneling/input surface
  after first sendCommand.
- Disallow store-meta for input cross process.
- Disallow emptyBuffer for surface input (via IOMX).
- Fix checking for input surface.

Bug: 29422020
Change-Id: I801c77b80e703903f62e42d76fd2e76a34e4bc8e