Fixes <https://issues.guix.gnu.org/64653>.
The ‘dynamic-wind’ was causing files to be closed prematurely when
leaving the dynamic extent of PROC for instance via a delimited
continuation, using Fibers (that ‘dynamic-wind’ call was also
semantically incorrect in the first place).
* gnu/services/shepherd.scm (shepherd-configuration-file)
[config](call-with-file): Remove.
(call-with-input-file, call-with-output-file): Rewrite in terms of
‘call-with-port’.
Change-Id: Ica8af71a04f525a15be99985552063cb98cd6ee8
4e431fda5f