Upgrade to HK2 2.5.0-b31

Memory leak in versions before HK2 2.5.0-b31:

* javaee/hk2#43
* javaee/hk2@bb2621c

pom.xml

@@ -105,7 +105,7 @@
         <guice.version>4.1.0</guice.version>
         <HdrHistogram.version>2.1.9</HdrHistogram.version>
         <hibernate-validator.version>5.3.4.Final</hibernate-validator.version>
-        <hk2.version>2.5.0-b30</hk2.version> <!-- The HK2 version should match the version being used by Jersey -->
+        <hk2.version>2.5.0-b31</hk2.version> <!-- The HK2 version should match the version being used by Jersey -->
         <jackson.version>2.8.5</jackson.version>
         <jadconfig.version>0.13.0</jadconfig.version>
         <java-semver.version>0.9.0</java-semver.version>