Refactor RouteDistinguisherUtil
This class is using deprecated ByteBufWriteUtils methods and this
patch refactors it not to, as it only brings invariant checks
to the table.
Serialize method made a dispatcher between the three distinct
implementations.
Each implementation is refactored to first check string validity
by searching for separators -- which is done faster than previous
String.split(String). Only after validation are parts split
and pushed to the buffer.
Change-Id: Ie87fbaf042d75176c584bf15e345c463b4c747f0
Signed-off-by: Robert Varga <robert.varga@pantheon.tech>