upgrade_test: increase operations number of entire workloads
upgrade_test: increase operations number of entire workloads

We added verify test after upgrading/rollbacking each node, each verify takes
about 5 mins. So increase the operations number of entire workloads, we wish
the entire workload covers the whole upgrade stage.

Signed-off-by: Amos Kong <eb01d8f828a6c9a20be4534e72e049aaf41503df@scylladb.com>

scylladb/scylla-longevity-tests,scylladb/scylla-cluster-tests,scylladb/scylla-cluster-tests,scylladb/scylla-longevity-tests,scylladb/scylla-cluster-tests,scylladb/scylla-cluster-tests,scylladb/scylla-cluster-tests,scylladb/scylla-longevity-tests