Allow burnin to take "-t plain" as an option
Allow burnin to take "-t plain" as an option

The burnin code deals with "-t plain", but the command line parser
doesn't allow that as an option. This patch fixes this issue.

Reviewed-by: ultrotter


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