There isn't any command to change this one the das.properties file has
been written.
One way to change this is to just edit the das.properties file to have
the desired FQDN.
If the node has not yet been created, you can choose the value for the
DAS that is stored in the das.properties file by using that value as the
--host option when the first instance on the node is created.
So if you have a multihomed host with names "a" (default) and "b" and
you want the DAS to be referenced by "b" from host "c", do:
asadmin create-node-ssh --nodehost c nodec
asadmin --host b create-instance --node nodec i1
This will cause "b" to be written to das.properties rather than "a".
Tom