Fixed bug of FlowAction variants.

  * InetAddressAction: Fixed bug that an IP address passed via JAXB
    was not set.
  * DlAddrAction: MAC address should be pretty-formatted.

Other changes:

  * Reduce code clone.
  * Add unit tests for FlowAction variants.

Change-Id: I1ab973f369591ea78434359901c987ad50228401
Signed-off-by: Shigeru Yasuda <s-yasuda@da.jp.nec.com>