We can't move-from in the loop because the subject will be empty in
all but the first iteration.
Fixes crash during node stratup:
"Exiting on unhandled exception of type 'runtime_exception': runtime error: Invalid token. Should have size 8, has size 0"
Fixes update_cluster_layout_tests.py:TestUpdateClusterLayout.simple_add_node_1_test (and probably others)
Signed-off-by: Tomasz Grabiec <tgrabiec@scylladb.com>