domain_conf.c: skip checking ZPCI address is incomplete if not present

domain_conf.c: skip checking ZPCI address is incomplete if not present

Commit 076591009ad1 ("conf: fix zPCI address auto-generation on
s390") is doing a check for virZPCIDeviceAddressIsIncomplete()
prior to checking if the device has a ZPCI address at all. This
results in errors like these when starting libvirt:

  error : virDomainDeviceInfoFormat:7527 : internal error:
  Missing uid or fid attribute of zPCI address

Fix it by moving virZPCIDeviceAddressIsIncomplete() after the
check done by virZPCIDeviceAddressIsPresent().

Fixes: 076591009ad11ec108521b52a4945d0f895fa160
Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com>
Reviewed-by: Andrea Bolognani <abologna@redhat.com>