Fixes a bug introduced with the Shepherd 0.9.2 upgrade in commit
1ba0e38267 whereby files opened by, say,
the 'start' method of 'urandom-seed', could leak into the execution
environment of some other service--e.g., 'term-tty4'.
* gnu/services/shepherd.scm (shepherd-configuration-file)[config]:
Override 'call-with-input-file' and 'call-with-output-file'.
66fdaf3677