Improve calculation of poll interval for replicas

Currently the polling for replication is fairly simply, but can lead to polling too often. As an example if you had the following config for commits:

<autoCommit>
    <maxTime>15000</maxTime>
    <openSearcher>false</openSearcher>
</autoCommit>

<autoSoftCommit>
    <maxTime>60000</maxTime>
</autoSoftCommit> 

The current logic would setup polling to be half of the autoCommit time, so poll every 7.5 seconds. However since a new searcher isn't opened, there will only be changes reflected every 60 seconds on the leader. We can make this logic a bit smarter knowing that the replication handler won't reflect changes until a new searcher is opened.