Workaround JDK-8056014

This commit works around JDK bug JDK-8056014 in the javac compiler.
This bug is impacting CI compilations on JDK 8u11 and 8u25.

core/src/main/java/org/elasticsearch/common/inject/util/Modules.java

@@ -135,7 +135,8 @@ public final class Modules {
         private final Set<Module> baseModules;
 
         private RealOverriddenModuleBuilder(Iterable<? extends Module> baseModules) {
-            this.baseModules = unmodifiableSet(newHashSet(baseModules));
+            HashSet<? extends Module> modules = newHashSet(baseModules);
+            this.baseModules = unmodifiableSet(modules);
         }
 
         @Override