tests: fix tests with Tarantool master

[oleg-jukovec]

Due to some update in Tarantool master, our tests broke. We need to fix it.

Steps:

1. Determinate a commit on Tarantool master that breaks our tests.
2. Update our tests according to changes if a problem in the tests itself.

or

2. Create a reproducer of the problem for the Tarantool team and create an issue in tarantool/tarantool.
3. Create a PR in tarantool/tarantool with the fix (optional).

Reproducer could looks like commands in the Tarantool console:

1. Create a user as in the test.
2. Add grants to user as in the test.
3. Login as the user.
4. Execute box.schema.user.grant with args as in tests.

[oleg-jukovec]

https://www.tarantool.io/en/doc/latest/contributing/building_from_source/