dcache-core: Move LeadershipListenerGroup for reusability

Motivation:

The LeadershipListenerGroup is used to notify several components of leadership changes via the HAServiceLeadershipManager for the HA Cleaner service. In order to reuse it for other services, it is useful for the class to be located in a central place.

Modification:

Moved the LeadershipListenerGroup class to dcache-core, where the HAServiceLeadershipManager and CuratorFrameworkAware interface resides.

Result:

Reusing the LeadershipListenerGroup for other services is possible. High availability as implemented for the Cleaner service can be transferred to other services.
Addition to patch #12441.

Target: master
Requires-notes: no
Requires-book: no
Patch: https://rb.dcache.org/r/12443/
Acked-by: Albert Rossi

modules/dcache-chimera/src/main/resources/org/chimera/chimera-cleaner.xml

@@ -118,7 +118,7 @@
         </property>
     </bean>
 
-    <bean id="baseleaderlistener-group" abstract="true" class="org.dcache.chimera.namespace.LeadershipListenerGroup">
+    <bean id="baseleaderlistener-group" abstract="true" class="org.dcache.cells.LeadershipListenerGroup">
         <description>Propagates leadership change notifications to managed listeners</description>
         <property name="leaderElectionAwareComponents">
             <set>

modules/dcache-chimera/src/main/java/org/dcache/chimera/namespace/LeadershipListenerGroup.java → modules/dcache/src/main/java/org/dcache/cells/LeadershipListenerGroup.java

@@ -16,7 +16,7 @@
  * You should have received a copy of the GNU Affero General Public License
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
-package org.dcache.chimera.namespace;
+package org.dcache.cells;
 
 import org.apache.curator.framework.recipes.leader.LeaderLatchListener;
 import org.slf4j.Logger;