util/disk_cache: close fd in the fallback path

util/disk_cache: close fd in the fallback path

There are multiple `goto path_fail` with an open fd, but none that go to
`fail:` without going through `path_fail:` first, so let's just move the
`close(fd)` there.

Signed-off-by: Eric Engestrom <eric.engestrom@intel.com>
Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>