I have had progress, and failure.
I clicked the button, waited, and the browser responded with a popup saying that the rebuild had completed successfully. Then, I reset the MD and the diskless boot proceeded successfully, running for what seemed like 10 minutes until the next automatic reboot. Then it failed again, as before, not being able to find initrd.img.
Looking in /usr/pluto/diskless/82/boot, the 4.2.0-27 files do not exist, as before. Further, the timestamps indicate that they do not seem to have been touched in the last half hour, as though they had been rebuilt as part of the webadmin fix.
Another observation: watching the messages scroll by during the second reboot, I saw lots of references to 3.16.0 but none to 4.2.0.
Help.
CDM
Here is the current state:
root@dcerouter:/usr/pluto/diskless/82/boot# ls -la
total 43884
drwxr-xr-x 2 root root 4096 Feb 10 15:19 .
drwxr-xr-x 20 root root 4096 Feb 10 15:07 ..
-rw-r--r-- 1 root root 1214709 Jun 28 2016 abi-3.16.0-77-generic
-rw-r--r-- 1 root root 176220 Jun 28 2016 config-3.16.0-77-generic
lrwxrwxrwx 1 root root 55 Feb 10 15:07 initrd.img -> /usr/pluto/diskless/82/boot/initrd.img-4.2.0-27-generic
-rw-r--r-- 1 root root 34156419 Feb 10 15:18 initrd.img-3.16.0-77-generic
-rw-r--r-- 1 root root 176500 Mar 12 2014 memtest86+.bin
-rw-r--r-- 1 root root 178176 Mar 12 2014 memtest86+.elf
-rw-r--r-- 1 root root 178680 Mar 12 2014 memtest86+_multiboot.bin
-rw-r--r-- 1 root root 2795312 Jun 28 2016 System.map-3.16.0-77-generic
lrwxrwxrwx 1 root root 52 Feb 10 15:07 vmlinuz -> /usr/pluto/diskless/82/boot/vmlinuz-4.2.0-27-generic
-rw-r--r-- 1 root root 6034368 Jun 28 2016 vmlinuz-3.16.0-77-generic
root@dcerouter:/usr/pluto/diskless/82/boot#