#mongod --help
...
Replication options:
--fastsync indicate that this instance is starting from a dbpath
snapshot of the repl peer
--autoresync automatically resync if slave data is stale
--oplogSize arg size limit (in MB) for op log
...

autoresync is put in replication options, not in master/slave options so it should work with replset. Adding autoresync=true brings no effect.