test: flaky box/before_replace.test.lua test

[avtikhon]

Tarantool version:
Tarantool 2.7.0-71-gf18ca1e67
Target: Darwin-x86_64-RelWithDebInfo
Build options: cmake . -DCMAKE_INSTALL_PREFIX=/usr/local -DENABLE_BACKTRACE=ON
Compiler: /Library/Developer/CommandLineTools/usr/bin/cc /Library/Developer/CommandLineTools/usr/bin/c++
C_FLAGS: -Wno-unknown-pragmas -fexceptions -funwind-tables -fno-omit-frame-pointer -fno-stack-protector -fno-common -msse2 -std=c11 -Wall -Wextra -Wno-strict-aliasing -Wno-char-subscripts -Wno-gnu-alignof-expression -Werror
CXX_FLAGS: -Wno-unknown-pragmas -fexceptions -funwind-tables -fno-omit-frame-pointer -fno-stack-protector -fno-common -msse2 -std=c++11 -Wall -Wextra -Wno-strict-aliasing -Wno-char-subscripts -Wno-invalid-offsetof -Wno-gnu-alignof-expression -Werror

OS version:
OSX 13

Bug description:
https://gitlab.com/tarantool/tarantool/-/jobs/864152554#L4098

artifacts.zip

results file checksum: 6379f11bde87b463059911b670a29906

[016] --- box/before_replace.result	Fri Nov 13 15:27:44 2020
[016] +++ /tmp/tnt/rejects/box/before_replace.reject	Sat Nov 21 00:44:32 2020
[016] @@ -100,7 +100,7 @@
[016]  old_tuple, new_tuple
[016]  ---
[016]  - [1, 3]
[016] -- [1, 1]
[016] +- [1]
[016]  ...
[016]  s:upsert({2, 2}, {{'=', 2, 2}})
[016]  ---

Steps to reproduce:

Optional (but very desirable):

• coredump
• backtrace
• netstat