SERVER-15535 Refactor jstests/replsets/rollback.js to use bridging.
SERVER-15535 Eliminate jstests/replsets/sync1.js, whose functionality is covered elsewhere.
SERVER-15527 Explain cleanup: use getPlanSummary/indexName helpers

No functional changes.
SERVER-15227 Fix uninitialized PlanSummaryStats member
SERVER-15527 Always collect opdebug stats for queries
SERVER-15535 Do not step down on reconfig if you remain electable.

If someone else ought to be elected, or you cannot see the majority, you will step
down soon enough, due to heart beats.