mark existing volumes as initialized
mark existing volumes as initialized

We updating existing migration to avoid changing volumes that were
created after rc was deployed. So that we only do that when we upgrade
to 2.8 from 2.7.4

Signed-off-by: Chris Hendrix <f9e38fc3e1ff46784bdcadbf77d17f93932faf2c@pivotal.io>

concourse/concourse,concourse/concourse,concourse/concourse,concourse/concourse,concourse/concourse