Keystore 2.0: Fixes in the legacy wrapper.

* Filter out invalid tags before passing them to the Keymaster device.
* Support negative timestamps for NOT_BEFORE/AFTER tags. Because the
  Keystore CTS test wants to create historic certificates predating
  Jan 1970.

Test: Keystore CTS tests.
Change-Id: I25a4440bf1318e9925f7a0c2ac481c29a56a412e
3 files changed