ssl-proxies: Fix CRL check race condition

JGlobus uses CRLs as if they were immutable objects, however when
using the Bouncy Castle provider, the ASN.1 parser uses lazy
evaluation internally, which means the X509CRL object is not
thread safe.

This bug was originally filed against JGlobus 1.8 in

http://lists.globus.org/pipermail/jglobus-dev/2009-December/000320.html

with a patch that we have used since in a dCache specific fork
of JGlobus 1.8.

This pull request represents a port of the patch to JGlobus 2. We haven't
used JGlobus 2 under high load situations and for long enough time to
know whether the bug can be reproduced, but I have no reason to believe
that JGlobus 2 should not suffer from the same problem.