ArpHandler emulator: Abolish IPv4 forwarding.

The base controller has moved IPv4 forwarding logic from arphandler to
simpleforwarding. So it also should be removed from ArpHandler emulator.

Change-Id: I8c58a3a0cfa4ee37d1060c8c1084bb1d73a08ae2
Signed-off-by: Shigeru Yasuda <s-yasuda@da.jp.nec.com>
Merge "ArpHandler emulator: Abolish IPv4 forwarding."