Fixes <http://bugs.gnu.org/18935>.
Reported by Mark H Weaver <mhw@netris.org>.
Previously, if tests/nar.scm ran concurrently with tests/gexp.scm, the
store item "foo" containing the string "Hello, world!" could be
deleted (via 'delete-paths') from the tests/nar.scm daemon while the
tests/gexp.scm daemon would still consider it live.
* tests/nar.scm ("restore-file-set (missing signature)"):
Use (random-text) rather than "Hello, world!", to avoid concurrent
deletion of store item "foo" used in tests/gexp.scm.
834ea02ad8