Uses TPM return codes.

Rollback_index funcs now all return 0 if succcess, nonzero if error.
(Note: not fully implemented; Luigi, please clean this up in a
subsequent CL)

LoadKernel() checks return codes from TPM funcs.

LoadKernel() only looks at versions from TPM in normal boot mode.

Review URL: http://codereview.chromium.org/2735004
4 files changed