Don't close h2 database when last connection is closed

We now explicitly shutdown the H2 database used for persistent caches.
Hence don't close the h2 database when the last connection is closed.

Release-Notes: Don't close h2 database when last connection is closed
Change-Id: I80be71c7205c0c037ec82c48794e4d07418bbad7
diff --git a/java/com/google/gerrit/server/cache/h2/H2CacheFactory.java b/java/com/google/gerrit/server/cache/h2/H2CacheFactory.java
index 039a33e..9b207ee 100644
--- a/java/com/google/gerrit/server/cache/h2/H2CacheFactory.java
+++ b/java/com/google/gerrit/server/cache/h2/H2CacheFactory.java
@@ -223,6 +223,7 @@
     if (h2AutoServer) {
       url.append(";AUTO_SERVER=TRUE");
     }
+    url.append(";DB_CLOSE_DELAY=-1");
     Duration refreshAfterWrite = def.refreshAfterWrite();
     if (has(def.configKey(), "refreshAfterWrite")) {
       long refreshAfterWriteInSec =