openssh: tests: Revert _PATH_LOCALBASE usage

[jlduran]

Summary

Commit 1f474190fc28 ("Replace literal uses of /usr/local in C sources
with _PATH_LOCALBASE") globally replaced all literal uses of /usr/local
with _PATH_LOCALBASE.

This replacement should not have been applied under crypto, particularly
in the OpenSSH regression test suite, as it introduces unnecessary
differences from upstream.

[se]

The patch to use _PATH_LOCALBASE should not have been applied to contrib software that has been imported verbatim.
Therefore, the src/contrib directory (and src/sys/contrib etc.) had been excluded, but the fact that other such files exist below src/crypto had been missed.

[jlduran]

In D61437#1409130, @se wrote:

The patch to use _PATH_LOCALBASE should not have been applied to contrib software that has been imported verbatim.
Therefore, the src/contrib directory (and src/sys/contrib etc.) had been excluded, but the fact that other such files exist below src/crypto had been missed.

Yes, thank you! I'll commit after 15.2-RELEASE is out.