network/virt/vxlan: add dstport option if ip supports it

Newer versions of 'iproute' complain about not set VxLAN
'dstport' option:

  vxlan: destination port not specified
  Will use Linux kernel default (non-standard value)
  Use 'dstport 4789' to get the IANA assigned value
  Use 'dstport 0' to get default and quiet this message

This message interferes with the actual test output. If 'iproute'
supports the option, set it when adding new VxLAN devices.

Signed-off-by: Alexey Kodanev <alexey.kodanev@oracle.com>
2 files changed