released, all of def_boot_osid,temp_boot_osid,next_boot_osid is cleared.
bootinfo currently uses the nodes free/alloc status to determine if the
node gets PXEWAIT, but will eventually switch to looking at the osids;
A node with no osids set (as will be when free) will go into PXEWAIT. This
will allow os_load of free nodes!

Change temporary locked pid/eid to a real pid/eid (emulab-ops/nfree-locked)
to avoid transient problems in tmcd, where isalive would cause tmcd to
core dump cause the reserved table had a nonexistent pid/eid setting.