Import OVF: Lock config with "lock" property

Import OVF: Lock config with "lock" property

Previously a VMID conflict was possible when creating a VM on another node
between locking the config with lock_config_full and writing to it for the
first time with write_config.

Using create_and_lock_config eliminates this possibility. This means that now
the "lock" property is set in the config instead of using flock only.

$param was empty when it was assigned the three values "name", "memory" and
"cores" before being assigned to $conf later on. Assigning those values
directly to $conf avoids confusion about what the two variables contain.

Signed-off-by: Dominic Jäger <d.jaeger@proxmox.com>