network: Convert managed property of hostdev-pci ports correctly

network: Convert managed property of hostdev-pci ports correctly

virNetworkForwardDef.managed is a bool but
virNetworkPortDef.hostdevpci.managed is a virTristateBool, which
means that the current code performs the following incorrect
conversion:

  false -> BOOL_ABSENT
  true  -> BOOL_YES

Using the virTristateBoolFromBool() helper solves the issue.

Fixes: 6cb0ec48bd95c95489a987e05a88e8bcf1f9109c
Signed-off-by: Andrea Bolognani <abologna@redhat.com>
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>