Revert "longevity: use 3 keyspaces with different CompactionStrategy"
Revert "longevity: use 3 keyspaces with different CompactionStrategy"

This reverts commit a7dababd7d66b97eb5734fc11b1bfe3e77fb4d03.

Conflicts:
    longevity_test.py

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