(DSS) PAdES validation is synchronized (only one request at time)

[Priit Reiser]

(DSS) PAdES validation is not thread safe. As a workaround, synchronization block is added which negatively affects the service throughput (especially in case of large files)

https://esig-dss.atlassian.net/browse/DSS-923

[Aare Nurm]

This issue is fixed with upgrade to DSS5.0 in SIVA 2.0 project.