rollback_after_enabling_majority_reads.js test should wait for restarted node to be in SECONDARY state before running stepUp command

The rollback_after_enabling_majority_reads.js tries to stepUp a node after restarting it. But even after awaitNodesAgreeOnPrimary, the restarted node could still be in STARTUP2 state. Thus, the subsequent replSetStepUp could fail because "because member is not currently a secondary".