I found 2 bugs in flow conversion routine in sal-compatibility.

1. A NullPointerException is always thrown when a flow entry that contains
IN_PORT match field value is installed via sal-compatibility.
sal-compatibility sets a string representation of AD-SAL NodeConnector ID
(e.g. "OF|2") to in-port in a flow entry. But it must be converted into
MD-SAL NodeConnectorId (e.g. "openflow:1:2").

2. An invalid MD-SAL match is created if zero is set in DL_VLAN match field.
If zero is set in DL_VLAN match field in a flow entry, it must match packets
without VLAN tag. Thus in that case false must be set to vlan-id-present field
in a MD-SAL flow entry.