srm: Fix asynchroneous job storage leak

The asynchroneous job storage fails to preserve the force flag when
collapsing several save calls. In case srm.persistence.enable.history
is false (the default), this could lead to incomplete data in the
database. This in case could lead to incomplete cleanup of upload
directories after an SRM restart.

The patch also renames the boolean parameter to something that I find
less confusing.

Target: trunk
Request: 2.10
Request: 2.9
Request: 2.8
Request: 2.7
Require-notes: yes
Require-book: no
Acked-by: Paul Millar <paul.millar@desy.de>
Patch: https://rb.dcache.org/r/7307/
(cherry picked from commit 98f21155a8927aae68a2619c3738bb31f0110fa1)
Merge pull request #841 from gbehrmann/fix/2.8/rb7307

srm: Fix asynchroneous job storage leak