The TLV_IE_Collection, just like the individual TLV classes, do
use their snake-style names when converting from binary to dict
using the to_dict() method. It is inconsistent (and a bug) to
expect the CamelCase names during encoding (from_dict). After all,
we want the output of to_dict() to be used as input to from_dict().
Change-Id: Iabd1ad98c3878659d123eef919c22ca824886f8a