pylib: fix list roll command to work at built time

rocks list roll command (which is used to generate the userguide)
now works even if the roll is not present in the database, so
we can build the userguide with the command line help at built
time.
built: prepdevel do not insert a node with hostname==localhost

prepdevel was inserting the frontend info inside the database
using the result of hostname as the FE hostname.
On batlab hostname==localhost and this confuses rocks command
line.