[Koha] Error staging MARC records

[Mark Alexander]

It turned out that the configuration issue was a missing tmp_path
entry in koha-conf.xml.  There was some information about
this in bugzilla 20428; it seems the Debian 9 has issues with /tmp.

Here are the relevant entries in my fixed koha-conf.xml:

 <upload_path>/var/lib/koha/rpl/uploads</upload_path>
 <tmp_path>/var/lib/koha/rpl/tmp</tmp_path>

After adding tmp_path I discovered that it wasn't sufficient to get
Koha to recognize the new tmp_path by doing the following:

  systemctl stop koha-common
  systemctl start koha-common

I had to reboot the machine for the change to be effective.  I suspect
this is a plack-related issue, and that it might have been sufficient
to restart plack.