AbstractIndexRestApiServlet: Fix resource leak warning

Eclipse is flagging resource leak warning:

  Resource leak: '<unassigned Closeable value>' is not closed at this
  location.

Change-Id: I10184b801e73d4e85cdf87837203d11e6675416f

src/main/java/com/ericsson/gerrit/plugins/highavailability/forwarder/rest/AbstractIndexRestApiServlet.java

diff --git a/src/main/java/com/ericsson/gerrit/plugins/highavailability/forwarder/rest/AbstractIndexRestApiServlet.java b/src/main/java/com/ericsson/gerrit/plugins/highavailability/forwarder/rest/AbstractIndexRestApiServlet.java
index 4456064..f9ec516 100644
--- a/src/main/java/com/ericsson/gerrit/plugins/highavailability/forwarder/rest/AbstractIndexRestApiServlet.java
+++ b/src/main/java/com/ericsson/gerrit/plugins/highavailability/forwarder/rest/AbstractIndexRestApiServlet.java
@@ -26,6 +26,7 @@
 import com.google.gson.Gson;
 import java.io.IOException;
 import java.io.InputStreamReader;
+import java.io.Reader;
 import java.util.Optional;
 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse;
@@ -99,9 +100,9 @@
   protected Optional<IndexEvent> parseBody(HttpServletRequest req) throws IOException {
     String contentType = req.getContentType();
     if (contentType != null && contentType.contains("application/json")) {
-      return Optional.ofNullable(
-          gson.fromJson(
-              new InputStreamReader(req.getInputStream(), Charsets.UTF_8), IndexEvent.class));
+      try (Reader reader = new InputStreamReader(req.getInputStream(), Charsets.UTF_8)) {
+        return Optional.ofNullable(gson.fromJson(reader, IndexEvent.class));
+      }
     }
     return Optional.empty();
   }