DFUPlus files should not automatically expire with default expiry days if no expireDays parameter present.

If there is not expireDays parameter for a DFUPlus action, then in the execution chain it gets the 0 value which means default expiration, however it should be -1 (no expiration).

NB: the PR for this JIRA changes prevents a default value of 0 being set in the esp service (ws_fs), which causes files to expire after the default (Sasha) number of days (expiryDays)