Clarify setup for parallel job execution performance test
Clarify setup for parallel job execution performance test

Explicitly state, that parallelism enhancing options are to be used
in parallel performance tests, if it is best practice to use them on
the respective versions. A prerequisite for those options is that
using them does not require, even under heavy load but assuming enough
capacity in the cluster, any jobs to be retried.

Signed-off-by: Klaus Aehlig <4ce51de36d9068cd7db2eec1151e0f3f95419008@google.com>
Reviewed-by: Hrvoje Ribicic <be5828fca31f89218048bec4189e30a581aa65da@google.com>

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