fix checkstyle

Author: JoaoJandre

api/src/main/java/org/apache/cloudstack/api/command/user/backup/DownloadValidationScreenshotCmd.java

@@ -17,19 +17,13 @@
 package org.apache.cloudstack.api.command.user.backup;
 
 import com.cloud.event.EventTypes;
-import com.cloud.exception.ConcurrentOperationException;
-import com.cloud.exception.InsufficientCapacityException;
 import com.cloud.exception.InvalidParameterValueException;
-import com.cloud.exception.NetworkRuleConflictException;
-import com.cloud.exception.ResourceAllocationException;
-import com.cloud.exception.ResourceUnavailableException;
 import com.cloud.user.Account;
 import org.apache.cloudstack.api.ACL;
 import org.apache.cloudstack.api.APICommand;
 import org.apache.cloudstack.api.ApiConstants;
 import org.apache.cloudstack.api.BaseAsyncCmd;
 import org.apache.cloudstack.api.Parameter;
-import org.apache.cloudstack.api.ServerApiException;
 import org.apache.cloudstack.api.response.BackupResponse;
 import org.apache.cloudstack.api.response.ExtractResponse;
 import org.apache.cloudstack.backup.Backup;