veyron/services/security/discharger: set pathInStore in constructor

Change-Id: I709ffa16b21b9731e4c84196d120b41192caad57
diff --git a/services/security/discharger/revoker.go b/services/security/discharger/revoker.go
index e945a37..174830a 100644
--- a/services/security/discharger/revoker.go
+++ b/services/security/discharger/revoker.go
@@ -82,7 +82,7 @@
 		return nil, fmt.Errorf("revoker.Revoker called more than once")
 	}
 	var err error
-	revocationService.revocationServiceT = new(revocationServiceT)
+	revocationService.revocationServiceT = &revocationServiceT{pathInStore: pathInStore}
 	revocationService.store, err = vstore.New(storeName)
 	if err != nil {
 		return nil, err