Marks talker as not present and removes attribute on a 
TA leave
Checks if full talker details are present before
adding the information
Fix for Test MSRP.End.c.35.1.5 — MSRPDU AttributeLength

Check the AttributeLength field matches the length for
that attribute type, else drop the rest of the PDU.
Fix for Test MSRP.End.c.35.1.6 — MSRPDU AttributeListLength

Checks for invalid AttributeListLengths and drops the PDU