Fix non-deterministic test failures

[CMoH]

Fix some build failures that appear on most builds with java8, and only spuriously on java7:

Running org.apache.archiva.rest.services.BrowseServiceTest
Tests run: 21, Failures: 1, Errors: 0, Skipped: 0, Time elapsed: 50.76 sec <<< FAILURE! - in org.apache.archiva.rest.services.BrowseServiceTest
metadatainbatchmode(org.apache.archiva.rest.services.BrowseServiceTest)  Time elapsed: 2.955 sec  <<< FAILURE!
java.lang.AssertionError: 

Expecting:
 <{"jenkins_version"="1.486", "author"="alecharp"}>
to contain:
 <[MapEntry[key='buildNumber', value='1']]>
but could not find:
 <[MapEntry[key='buildNumber', value='1']]>

        at org.apache.archiva.rest.services.BrowseServiceTest.metadatainbatchmode(BrowseServiceTest.java:431)