burnin: redo the output formatting
burnin: redo the output formatting

Since we added many more tests in burnin, the output became almost
unreadable. This patch changes the output to an indented one, so that
the different phases and operations of burnin are more easily
understood.

Reviwed-by: ultrotter

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