Replace most usages of PacketLineIn.END with PacketLineIn.end()

Replace most usages of PacketLineIn.END with PacketLineIn.end()

PacketLineIn.END is only referenced in tests. Replace most of those
with a new package visible end() method.

Remaining usages of PacketLineIn.END are in the form:

  while ((line = pckIn.readString()) != PacketLineIn.END) {

and are not trivial replacements, hence are not touched in this change.

Change-Id: Id77c5321ddcad127130b246bde8f08736e60e1ea
Signed-off-by: David Pursehouse <david.pursehouse@gmail.com>