db: initialize bigint, boolean columns

gorp hates nil.

db/migrations/0002_dex_admin.sql

@@ -1,2 +1,4 @@
 -- +migrate Up
 ALTER TABLE client_identity ADD COLUMN "dex_admin" boolean;
+
+UPDATE "client_identity" SET "dex_admin" = false;

db/migrations/0003_user_created_at.sql

@@ -1,2 +1,4 @@
 -- +migrate Up
 ALTER TABLE authd_user ADD COLUMN "created_at" bigint;
+
+UPDATE authd_user SET "created_at" = 0;

functional/repo/testutil.go

@@ -22,6 +22,8 @@ func initDB(dsn string) *gorp.DbMap {
 		panic(fmt.Sprintf("Unable to drop migration table: %v", err))
 	}
 
-	db.MigrateToLatest(c)
+	if _, err = db.MigrateToLatest(c); err != nil {
+		panic(fmt.Sprintf("Unable to migrate: %v", err))
+	}
 	return c
 }