PeerSync requests information on the most recent nUpdates updates from another instance to determine whether PeerSync can succeed. The value of nUpdates can be customized in solrconfig.xml: UpdateHandler.UpdateLog.NumRecordsToKeep.
PeerSync can be initiated in a number of different paths. One path to start PeerSync (leader-initiated sync) is incorrectly still using a hard-coded value of nUpdates=100.
This change fixes leader-initiated-sync code path to also pick up the value of nUpdates from the customized/configured value.