jaxb plugin failure workaround when using jdk8
use linked hash map to preserve ordering for test diff comparison

failure introduced by http://openjdk.java.net/jeps/180

"This change will likely result in a change to the iteration order of the HashMap class. The HashMap specification explicitly makes no guarantee about iteration order. The iteration order of the LinkedHashMap class will be maintained."
Merge pull request #416 from sonatype/NEXUS-6340-jdk8-build

NEXUS-6340 jdk8 build

merging based on scrum discussion last week that both changes were ok for now.