Call the callback on success in new verifier in a compatible way

Call the callback on success in new verifier in a compatible way
when we succeed with a chain, and ensure we do not call the callback
twice when the caller doesn't expect it.  A refactor of the end of
the legacy verify code in x509_vfy is probably overdue, but this
should be done based on a piece that works. the important bit here
is this allows the perl regression tests in tree to pass.

Changes the previously committed regress tests to test the success
case callbacks to be known to pass.

ok bluhm@ tb@