hashing: fix performance regression
hashing: fix performance regression

benchmarks before:
 consistent-hashing  deplication_factor: 1 diverse_replicas: 1 n_destinations: 1     datapoints: 100000 msecs: 36
 consistent-hashing  deplication_factor: 1 diverse_replicas: 1 n_destinations: 16    datapoints: 100000 msecs: 735
 consistent-hashing  deplication_factor: 1 diverse_replicas: 1 n_destinations: 32    datapoints: 100000 secs: 2.18479
 consistent-hashing  deplication_factor: 1 diverse_replicas: 1 n_destinations: 48    datapoints: 100000 secs: 5.39408

benchmarks after:
 consistent-hashing  replication_factor: 1 diverse_replicas: 1 n_destinations: 1     datapoints: 100000 msecs: 44
 consistent-hashing  replication_factor: 1 diverse_replicas: 1 n_destinations: 16    datapoints: 100000 msecs: 483
 consistent-hashing  replication_factor: 1 diverse_replicas: 1 n_destinations: 32    datapoints: 100000 msecs: 871
 consistent-hashing  replication_factor: 1 diverse_replicas: 1 n_destinations: 48    datapoints: 100000 secs: 1.36102

obfuscurity/carbon,criteo-forks/carbon,deniszh/carbon,deniszh/carbon,graphite-project/carbon,piotr1212/carbon,graphite-project/carbon,criteo-forks/carbon,obfuscurity/carbon,piotr1212/carbon