test: flaky box/on_replace.test.lua test

[avtikhon]

Tarantool version:
Tarantool 2.5.0-32-g7f20272ea
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 -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 -Werror

OS version:
OSX

Bug description:
https://gitlab.com/tarantool/tarantool/-/jobs/556348765

 [059] --- box/on_replace.result	Sun May 17 15:37:55 2020
 [059] +++ box/on_replace.reject	Mon May 18 05:08:43 2020
 [059] @@ -682,15 +682,15 @@
 [059]  ...
 [059]  s2:select()
 [059]  ---
 [059] -- - [1, 2]
 [059] -  - [2, 4]
 [059] -  - [3, 6]
 [059] +- - [1]
 [059] +  - [2]
 [059] +  - [3]
 [059]  ...
 [059]  s3:select()
 [059]  ---
 [059] -- - [1, 1]
 [059] -  - [2, 3]
 [059] -  - [3, 5]
 [059] +- - [1]
 [059] +  - [2]
 [059] +  - [3]
 [059]  ...
 [059]  s1:drop()
 [059]  ---

Steps to reproduce:

Optional (but very desirable):

• coredump
• backtrace
• netstat