change INPORT action to IN_PORT (spec-wise)

Originally filed as OPNFLWPLUG-263
https://bugs.opendaylight.org/show_bug.cgi?id=1725 in Helium, and the request was to make this an enhancement for Lithium.

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When I try to create a flow via restconf with IN_PORT as the action I see that no flow mod is sent to the corresponding switch (via pkt capture on mininet vm running OVS). Also in the OSGI console, the following errors are seen:

2014-09-05 14:58:33.456 PDT [OFRpc-2] ERROR o.o.o.o.m.c.s.c.ActionConvertor - Invalid Port specified null for Output Action for OF version:OF13
2014-09-05 14:58:33.456 PDT [OFRpc-2] ERROR o.o.o.o.m.c.s.c.ActionConvertor - Invalid Port specified null for Output Action for OF version:OF13
2014-09-05 14:58:33.456 PDT [nioEventLoopGroup-12-6] WARN o.o.o.protocol.impl.core.OFEncoder - Message serialization failed: null

Here is the flow_mod XML:

<flow xmlns="urn:opendaylight:flow:inventory"><instructions><instruction><order>0</order><apply-actions><action><order>0</order><output-action><output-node-connector>IN_PORT</output-node-connector></output-action></action></apply-actions></instruction></instructions><match><ethernet-match><ethernet-type><type>0x800</type></ethernet-type><ethernet-source><address>00:ab:cd:ef:01:23</address></ethernet-source><ethernet-destination><address>ff:ff:ff:ff:ff:ff</address></ethernet-destination></ethernet-match><ipv4-source>11.3.0.0/16</ipv4-source><ipv4-destination>99.0.0.0/8</ipv4-destination></match><strict>false</strict><hard-timeout>60</hard-timeout><idle-timeout>30</idle-timeout><flow-name>No Name</flow-name><priority>0</priority><barrier>false</barrier><cookie>0</cookie><cookie_mask>0</cookie_mask><table_id>22</table_id><id>161</id></flow>

If it matters, the REST details are a PUT @ /restconf/config/opendaylight-inventory:nodes/node/openflow:1/table/22/flow/161

Attached are some robot test logs if it helps.