test: don't leave open read views after vinyl/errinj_tx

See commit 65061cb4 ("test: don't leave open read views after
vinyl/iterator") for more details.

Follow-up #3862

test/vinyl/errinj_tx.result

@@ -433,3 +433,13 @@ last_read
 space:drop()
 ---
 ...
+-- Collect all iterators to make sure no read views are left behind,
+-- as they might disrupt the following test run.
+collectgarbage()
+---
+- 0
+...
+box.stat.vinyl().tx.read_views -- 0
+---
+- 0
+...

test/vinyl/errinj_tx.test.lua

@@ -192,3 +192,8 @@ while f2:status() ~= 'dead' do fiber.sleep(0.01) end
 last_read
 
 space:drop()
+
+-- Collect all iterators to make sure no read views are left behind,
+-- as they might disrupt the following test run.
+collectgarbage()
+box.stat.vinyl().tx.read_views -- 0