Fix schedule install DAO issue

(cherry picked from commit 4dee16dffb)

components/application-mgt/org.wso2.carbon.device.application.mgt.core/src/main/java/org/wso2/carbon/device/application/mgt/core/util/DAOUtil.java

@@ -274,7 +274,7 @@ public class DAOUtil {
             }
 
             subscription.setStatus(ExecutionStatus.valueOf(rs.getString("STATUS")));
-            subscription.setScheduledAt(rs.getTimestamp("SCHEDULED_AT").getTime());
+            subscription.setScheduledAt(rs.getLong("SCHEDULED_AT"));
             subscription.setScheduledBy(rs.getString("SCHEDULED_BY"));
             subscription.setDeleted(rs.getBoolean("DELETED"));
             subscriptionDTOS.add(subscription);