chimera: on shutdown propagate close to DB specific driver

Motivation:
If chimera DB driver is statefull it might require an explicit close on
shutdown.

Modification:
Add FsSqlDriver#close method that is called by JdbcFs#close.

Result:
better handling of db resources.

Acked-by: Paul Millar
Target: master
Require-book: no
Require-notes: no

modules/chimera/src/main/java/org/dcache/chimera/FsSqlDriver.java

@@ -86,7 +86,7 @@
 /**
  * SQL driver
  */
-public class FsSqlDriver {
+public class FsSqlDriver implements AutoCloseable {
     /**
      * Simple class to hold a tag assignment's directory inumber and its value.
      */
@@ -2436,4 +2436,12 @@ Integer getQoSPolicyId(String name) throws SQLException {
         }
         return _jdbc.queryForObject("SELECT id FROM t_qos_policy WHERE name=?", Integer.class, name);
     }
+
+    /**
+     * Close driver and free DB resources.
+     */
+    @Override
+    public void close() {
+        // to be overwritten by subclasses
+    }
 }

modules/chimera/src/main/java/org/dcache/chimera/JdbcFs.java

@@ -1539,6 +1539,7 @@ public String getInfo() {
     @Override
     public void close() throws IOException {
         maintenanceTaskExecutor.shutdown();
+        _sqlDriver.close();
     }
 
     @Override