LDAP: always store the certificate from the request
Store the certificate used to lookup a user as mapped attribute in the
cached user object.
Related to https://pagure.io/SSSD/sssd/issue/3050
Reviewed-by: Jakub Hrozek <jhrozek@redhat.com>
Reviewed-by: Lukáš Slebodník <lslebodn@redhat.com>