test(backup): mock BackupDetailsDao to fix NPE in NASBackupProviderTest

Adds @mock injection for BackupDetailsDao so NASBackupProvider's
backupDetailsDao field is wired during testDeleteBackup and
takeBackupSuccessfully, fixing the NPE flagged by @harikrishna-patnala.

Author: jmsperu

plugins/backup/nas/src/test/java/org/apache/cloudstack/backup/NASBackupProviderTest.java

@@ -52,6 +52,7 @@
 import com.cloud.vm.dao.VMInstanceDao;
 
 import org.apache.cloudstack.backup.dao.BackupDao;
+import org.apache.cloudstack.backup.dao.BackupDetailsDao;
 import org.apache.cloudstack.backup.dao.BackupRepositoryDao;
 import org.apache.cloudstack.backup.dao.BackupOfferingDao;
 import org.apache.cloudstack.storage.datastore.db.PrimaryDataStoreDao;
@@ -96,6 +97,9 @@ public class NASBackupProviderTest {
     @Mock
     private VMSnapshotDao vmSnapshotDaoMock;
 
+    @Mock
+    private BackupDetailsDao backupDetailsDao;
+
     @Test
     public void testDeleteBackup() throws OperationTimedoutException, AgentUnavailableException {
         Long hostId = 1L;