Revert "Revert "SERVER-6071 use command on local.slaves instead of cursor""

This reverts commit 6486b4035c5ac52679eb3e1a034c925ccdd20deb.
SERVER-6071 Use command on local.slaves instead of cursor

rearranged locking to prevent deadlocks
syncSourceFeedback methods use OIDs instead of BSONObj containing OIDs now
wrapped percolate so that it is not called when it is not needed