Use proper name for user-data file

Also add otaeguis ssh key to list
Pickup spantree branch until someday

The current release of the nexus module does not support a different
root directory appropiately, so to avoid issues use Spantree's fork
Change nexus root to avoid permission issues.

Nexus use java prefs, by default the $nexus_root directory is owned by
root, so to avoid lots of warnings in the logs change to something owned
by the nexus user