for slurpd's replica directory (slurpd.status, and rej file) use a subdir of what...

for slurpd's replica directory (slurpd.status, and rej file) use a subdir of what the user specifies (add replica/ to it) to avoid /tmp races. A lot of the files that slurpd uses cannot be opened with O_EXCL, nor can we safely determine if there are any hardlinks from another file to it, so we create our own subdirectory so we can control the perms, even in /tmp