Well,
I blindly tried the following:
* check the name of the block device used for metadata
* then shutdown the engine vm
* then stop agent and broker on first host
and finally zeroed the block device with
dd if=/dev/zero of=/dev/dm-12
(dm-12 is the block device pointed by metadata file)
started again broker and agent, after a while the engine
was started by HA and the metadata was readable.
now hosted_engine --vm-status works ok and I was able
to add a 2nd node to the cluster.
Maybe the metadata block device needs to be cleared when doing iSCSI setup?
Don't know if this is correct, but seems to work ok now.
Regards,
Matteo