ftp: Log CertPath in case CertPath validation fails

Addresses the issue that if authentication fails with a certificate
chain validation error, the error message contains absolutely no
information about the certificate that triggered the failure.

Requires https://github.com/gbehrmann/JGlobus/tree/feature/certpathvalidationexception_includes_certpath

Target: trunk
Request: 2.6
Request: 2.5
Request: 2.2-sha2
Require-notes: yes
Require-book: no
Acked-by: Paul Millar <paul.millar@desy.de>
Patch: http://rb.dcache.org/r/5543/
(cherry picked from commit ae2c685b6e98bacd2db15aa3ec18ca1e4bbb9e45)
Merge pull request #23 from gbehrmann/fix/2.6/certpathvalidationexception

ftp: Log CertPath in case CertPath validation fails