Added 5 server status metrics:
repl.syncSource.numSelections: The number of times a node attempted to choose a node to sync from among the available sync source options. This occurs if we re-evaluate our sync source, receive an error from the source, or step down.
repl.syncSource.numTimesChoseSame: The number of times a node kept it's original sync source after re-evaluating if its current sync source was optimal.
repl.syncSource.numTimesChoseDifferent: The number of times a node chose a new sync source after re-evaluating if its current sync source was optimal.
repl.syncSource.numTimesCouldNotFind: The number of times a node could not find a sync source when choosing a node to sync from among the available options.
repl.network.replSetUpdatePosition.num: The number of replSetUpdatePosition commands a node sent to its sync source.