satellite/audit: add missing logs for audit failure conditions

Among other conditions, nodes fail audits by returning incorrect
data and by reaching the max reverify count, but we weren't logging
these events. This commit adds the missing logs.

Change-Id: I80749a7e95e8cb97bc8dd7dac1e523e223114b7f

satellite/audit/reporter.go

@@ -213,8 +213,12 @@ func (reporter *Reporter) recordPendingAudits(ctx context.Context, pendingAudits
 				failed = append(failed, pendingAudit)
 				errlist.Add(err)
 			}
+			reporter.log.Info("Audit pending",
+				zap.Stringer("Piece ID", pendingAudit.PieceID),
+				zap.Stringer("Node ID", pendingAudit.NodeID))
 		} else {
 			// record failure -- max reverify count reached
+			reporter.log.Info("max reverify count reached (audit failed)", zap.Stringer("Node ID", pendingAudit.NodeID))
 			updateRequests = append(updateRequests, &overlay.UpdateRequest{
 				NodeID:       pendingAudit.NodeID,
 				AuditOutcome: overlay.AuditFailure,

satellite/audit/verifier.go

@@ -233,6 +233,8 @@ func (verifier *Verifier) Verify(ctx context.Context, path storj.Path, skip map[
 	}
 
 	for _, pieceNum := range pieceNums {
+		verifier.log.Info("Verify: share data altered (audit failed)",
+			zap.Stringer("Node ID", shares[pieceNum].NodeID))
 		failedNodes = append(failedNodes, shares[pieceNum].NodeID)
 	}