fix(latency.py): change all latency values to be float
fix(latency.py): change all latency values to be float

part of the number were being saved as strings instead
of float numbers, and with the new index in the ES it
will most likely not work, hence enforcing all latency
results to be numbers now.

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