test: flaky replication-py/conflict test on OSX

[avtikhon]

Tarantool version:
Tarantool 2.5.0-27-g32f59756a
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 14, 15

Bug description:

 [005] --- replication-py/conflict.result	Tue Feb 25 14:59:45 2020
 [005] +++ replication-py/conflict.reject	Fri May 15 06:10:01 2020
 [005] @@ -27,7 +27,7 @@
 [005]  replication state is correct
 [005]  box.space.test:select{1}
 [005]  ---
 [005] -- - [1, 4]
 [005] +- - [1, 2]
 [005]  ...
 [005]  box.space.test:select{1}
 [005]  ---

Steps to reproduce:

Optional (but very desirable):

• coredump
• backtrace
• netstat