Error deploying administration application pool credentials. Another deployment may be active. An object of the type Microsoft.SharePoint.Administration.SPAdminAppPoolCredentialDeploymentJobDefinition named "job-admin-apppool-change" already exists under the parent Microsoft.SharePoint.Administration.SPTimerService named "SPTimerV4". Rename your object or delete the existing object.
This error indicates that either some timer job is running or scheduled but while checking in the Central Administration I found nothing.
Later after searching for some time I found that the SharePoint Timer Service was not running.