Check for proper code for access errors

[roman-khimov]

All tests that check for access violations should get error code 2048 in reply and this needs to be checked for.

Refs. nspcc-dev/neofs-node#4052

[roman-khimov]

Related to #919

[roman-khimov]

Fixed now, waiting for test results.

[roman-khimov]

Here we go: https://rest.fs.neo.org/Aku38wpn2xEqfEPxmwyAa7N3VnAkMV8PEVkpLqwKM1z3/5586-1783426571/index.html#

I expected more of them. Either session tokens are rare in our tests or we don't have error codes checked somewhere.