ofproto: Implement OF1.4 Set/Get asynchronous configuration messages.

ofproto: Implement OF1.4 Set/Get asynchronous configuration messages.

This patch adds support for Openflow1.4 set/get asynchronous configuration
messages. OpenVSwitch already supports set/get asynchronous configuration
messages for Openflow1.3. In this patch OFPT_SET_ASYNC_CONFIG message
allows the controllers to set the configuration for OFPT_ROLE_STATUS,
OFPT_TABLE_STATUS and OFPT_REQUESTFORWARD in addition to the Openflow1.3
messages. In a OFPT_SET_ASYNC, only the properties that shall be changed
need to be included, properties that are omitted from the message are
unchanged.

The OFPT_GET_ASYNC_CONFIG is used to query the asynchronous configuration
of switch. In a OFPT_GET_ASYNC_REPLY message, all properties must be
included.

According to Openflow1.4 the initial configuration shall be:

   - In the “master” or “equal” role, enable all OFPT_PACKET_IN messages,
     except those with reason OFPR_INVALID_TTL, enable all OFPT_PORT_STATUS
     and OFPT_FLOW_REMOVED messages, and disable all OFPT_ROLE_STATUS,
     OFPT_TABLE_STATUS and OFPT_REQUESTFORWARD messages.

   - In the “slave” role, enable all OFPT_PORT_STATUS messages and disable
     all OFPT_PACKET_IN, OFPT_FLOW_REMOVED, OFPT_ROLE_STATUS,
     OFPT_TABLE_STATUS and OFPT_REQUESTFORWARD messages.

Signed-off-by: Niti Rohilla <niti.rohilla@tcs.com>
Signed-off-by: Ben Pfaff <blp@nicira.com>