Tries to discover user proxy location.
If a UID system property is set, and running on a Unix machine it
returns /tmp/x509up_u${UID}. If any other machine then Unix, it returns
${tempdir}/x509up_u${UID}, where tempdir is a platform-specific
temporary directory as indicated by the java.io.tmpdir system property.
If a UID system property is not set, the username will be used instead
of the UID. That is, it returns ${tempdir}/x509up_u_${username}
Discovers location of ca certificates directory.
First the ${user.home}/certificates directory is checked.
If the directory does not exist, and on a Unix machine, the
/etc/grid-security/certificates directory is checked next. If
That directory does not exist and GLOBUS_DEPLOY_PATH or
GLOBUS_INSTALL_PATH variables are set then the share directories
are also checked. Otherwise, null is returned.
This indicates the the certificates directory could
not be found.