When querying all paths in a binary cache store, the path's representation
is `<hash>-x` (where `x` is the value of `MissingName`) because the .narinfo
filenames only contain the hash.
Before cc46ea1630 this worked correctly,
because the entire path info was read and the path from this
representation was printed, i.e. in the form `<hash>-<name>`. Since then
however, the direct result from `queryAllValidPaths()` was used as `path`.
Added a regression test to make sure the behavior remains correct.
(cherry picked from commit c80cd6bb06)
cb7beb05cd