If a timestamp was larger than the max epoch value was sent via
graphite it would cause the timestamp to overflow when it was
marshaled/unmarshaled back from the raft log. The overflow cause
the shard group to get created with the wrong timestamp which cause
a panic when writing the point. The panic was caused because the
timestamp that were supposed to exists in a map created by MapShards
did not actually exist so a nil ShardGroup was used.
The change prevents creating the point with an invalid timestamp. Since
graphite using a timestamp in seconds, the maximum range is known and
can be prevented. This also adds a check for the minimum range as well.
Fixes#3785
73510a0a68