test: make simple_operations_test compatible with Tarantool 2.8

After tarantool/tarantool#3378 it's
possible to perform updates with gaps. So one of testcases that
returned an error became irrelevant for 2.8+. This patch checks
that update is valid for new Tarantool versions.

Also it's not complete 2.8 support because of a bug
tarantool/tarantool#6069. But since
issue has been already resolved we should just wait for update.

Author: olegrok

test/integration/simple_operations_test.lua

@@ -426,8 +426,16 @@ pgroup:add('test_intermediate_nullable_fields_update', function(g)
         }
     })
 
-    -- This tests use jsonpath updates.
-    if _TARANTOOL >= "2.3" then
+    -- Test uses jsonpaths so it should be run for version 2.3+
+    -- where jsonpaths are supported (https://github.com/tarantool/tarantool/issues/1261).
+    -- However since 2.8 Tarantool could update intermediate nullable fields
+    -- (https://github.com/tarantool/tarantool/issues/3378).
+    -- So before 2.8 update returns an error but after it update is correct.
+    if _TARANTOOL > "2.8" then
+        local _, err = g.cluster.main_server.net_box:call('crud.update',
+            {'developers', 1, {{'=', '[5].a.b[1]', 3}, {'=', 'extra_5', 'extra_value_5'}}})
+        t.assert_equals(err, nil)
+    elseif _TARANTOOL >= "2.3" then
         local _, err = g.cluster.main_server.net_box:call('crud.update',
             {'developers', 1, {{'=', '[5].a.b[1]', 3}, {'=', 'extra_5', 'extra_value_5'}}})
         t.assert_equals(err.err, "Failed to update: Field ''extra_5'' was not found in the tuple")