burnin: update migration to latest log formatting
burnin: update migration to latest log formatting

Reviewed-by: ultrotter

ganeti-github-testing/ganeti-test-1,yiannist/ganeti,leshchevds/ganeti,grnet/snf-ganeti,onponomarev/ganeti,yiannist/ganeti,grnet/snf-ganeti,ganeti-github-testing/ganeti-test-1,apyrgio/ganeti,leshchevds/ganeti,andir/ganeti,andir/ganeti,andir/ganeti,bitemyapp/ganeti,ganeti/ganeti,mbakke/ganeti,ganeti/ganeti,bitemyapp/ganeti,apyrgio/snf-ganeti,ganeti/ganeti,yiannist/ganeti,onponomarev/ganeti,apyrgio/snf-ganeti,dimara/ganeti,leshchevds/ganeti,mbakke/ganeti,mbakke/ganeti,dimara/ganeti,apyrgio/ganeti