securID code fixes

securID code fixes

Fixes to get securID preauth plugin working. A separate patch will
address error handling and build issues.

* Permit a preauth plugin to return KRB5KDC_ERR_PREAUTH_REQUIRED from
  the verify entry point.

* If verify_securid2 fails, save the return value and return that
  rather than success after dealing with encoding the out_edata

* Use the client key not the securid principal key for the sam
  checksum

* indicate that securID is hardware authentication

ticket: 6805
target_version: 1.9
tags: pullup

git-svn-id: svn://anonsvn.mit.edu/krb5/trunk@24465 dc483132-0cff-0310-8789-dd5450dbe970