Apply SDLS to USLP Primary Header

[ThirteenFish]

SDLS 3.2.2.5 specifies that:

The USLP ApplySecurity Payload shall consist of the portion of the USLP Transfer Frame from the first octet of the Transfer Frame Primary Header to the last octet of the Transfer Frame Data Field.

See also SDLS 5.4 for a concise diagram and 4.2.3.4 for method of operation.

We only apply it to the Data Field, but not the Primary Header. There's some provisions (SDLS 4.2.2.6.2) for masking off portions of the payload for authentication but we really want to include all of it.

Also SDLS authentication has a mandatory security header that we don't implement (SDLS 4.1.1, 4.2.3.4). It'd be nice for correctness to have it, but that's a bigger EDL protocol change than the above.