Unwanted network disk mounts
Further to my automounting network disk woes:
Zapping PRAM doesn't work either, nor does playing with what shows in the sidebar of Finder windows among the Bonjour, Connected Server, and Shared sections of Finder prefs, but.....

I might have just found the answer, and it's weird. I had noticed that opening Preview or TextEdit would always mount these network disks, and those two apps, in Apple's infinite wisdom, start up with an Open... dialog set to one's Documents folder. I had made aliases of the two disks and placed those aliases in my Documents folder. By dragging them to my Dock I had a clickable icon for each that showed them to be network disks (just dragging the icon of the mounted disk directly to the Dock shows them with a generic folder icon). I wondered if the Open dialog of Preview was mounting the disks as part of showing what was available in Documents for it to open, so I dragged the aliases onto the Desktop. The disks still mounted, so I tried a restart to see if Preview would still do it. It did. So then I cleared the System cache, all user caches and restarted again. This time the disks didn't mount! Being either brave or foolish, I dragged the aliases back into the Documents folder, and they still don't mount on opening Preview! I have restarted since just to see if they would reappear on opening Preview, but they don't. It's odd how this has happened immediately on upgrade to 10.10 and again with 10.11. With 10.10 it went away with a 10.10.x upgrade, but this time I may have solved it