Make TPM owner clear optional for factory_TPM.

The test now has two control files:
  control - Does not clear the TPM, may be run repeatedly.
  control.with_tpm_clear - Clears the TPM at the end of the test.

BUG=chrome-os-partner:19962
TEST=Ran both control files

Change-Id: I1be82f6dd3676ddd2391956a4e16c58474965318
Reviewed-on: https://gerrit.chromium.org/gerrit/58553
Reviewed-by: Darren Krahn <[email protected]>
Tested-by: Darren Krahn <[email protected]>
Commit-Queue: Darren Krahn <[email protected]>
3 files changed