java_gen: fix bug in IPv4Address.equals / hashCode

IPv4Address's equals and hashCode were mistakenly considering
the ephemeral bytesCache array for equals() and hashCode().
Thanks, Sudeep for the catch.
Merge into master from pull request #194:
java_gen: fix bug in IPv4Address.equals / hashCode (https://github.com/floodlight/loxigen/pull/194)