fixed build - cleaned up the use of guava Maps

Original commit: elastic/x-pack-elasticsearch@05b2dc4c57

shield/src/main/java/org/elasticsearch/shield/authc/esusers/tool/ESUsersTool.java

@@ -389,7 +389,7 @@ public class ESUsersTool extends CliTool {
             roles.addAll(Arrays.asList(addRoles));
             roles.removeAll(Arrays.asList(removeRoles));
 
-            Map<String, String[]> userRolesToWrite = Maps.newHashMapWithExpectedSize(userRoles.size());
+            Map<String, String[]> userRolesToWrite = new HashMap<>(userRoles.size());
             userRolesToWrite.putAll(userRoles);
             if (roles.size() == 0) {
                 userRolesToWrite.remove(username);