Fix tx_conflict.test

Some verification spaces (q1 and q2) are not truncated before
every test round and that sometimes causes wrong results.

Fix it.

test/vinyl/tx_conflict.result

@@ -126,6 +126,10 @@ function prepare()
     end
     s1:truncate()
     s2:truncate()
+    if ignore_unnecessary_conflict1 then
+        q1:truncate()
+        q2:truncate()
+    end
     for i=1,num_key do
         local r = math.random(5)
         local v = get_unique_value()

test/vinyl/tx_conflict.test.lua

@@ -95,6 +95,10 @@ function prepare()
     end
     s1:truncate()
     s2:truncate()
+    if ignore_unnecessary_conflict1 then
+        q1:truncate()
+        q2:truncate()
+    end
     for i=1,num_key do
         local r = math.random(5)
         local v = get_unique_value()