test: flaky replication/gh-4605-empty-password.test.lua test

[avtikhon]

Tarantool version:
Tarantool 2.5.0-73-g5ca12a4
Target: Linux-x86_64-RelWithDebInfo
Build options: cmake . -DCMAKE_INSTALL_PREFIX=/usr/local -DENABLE_BACKTRACE=ON
Compiler: /usr/bin/cc /usr/bin/c++
C_FLAGS: -static-libstdc++ -fexceptions -funwind-tables -fno-omit-frame-pointer -fno-stack-protector -fno-common -fopenmp -msse2 -std=c11 -Wall -Wextra -Wno-strict-aliasing -Wno-char-subscripts -Wno-format-truncation -fno-gnu89-inline -Wno-cast-function-type
CXX_FLAGS: -static-libstdc++ -fexceptions -funwind-tables -fno-omit-frame-pointer -fno-stack-protector -fno-common -fopenmp -msse2 -std=c++11 -Wall -Wextra -Wno-strict-aliasing -Wno-char-subscripts -Wno-format-truncation -Wno-invalid-offsetof -Wno-cast-function-type

OS version:
Linux

Bug description:
https://gitlab.com/tarantool/tarantool/-/jobs/564557070

 [047] --- replication/gh-4605-empty-password.result	Mon Feb 24 17:54:36 2020
 [047] +++ replication/gh-4605-empty-password.reject	Fri May 22 23:34:39 2020
 [047] @@ -37,7 +37,42 @@
 [047]   | ...
 [047]  i.replication[i.id % 2 + 1].upstream.status == 'follow' or i
 [047]   | ---
 [047] - | - true
 [047] + | - version: 2.5.0-73-g5ca12a4
 [047] + |   id: 2
 [047] + |   ro: false
 [047] + |   uuid: f990adde-8807-4921-942c-143717974b42
 [047] + |   package: Tarantool
 [047] + |   cluster:
 [047] + |     uuid: 70d3c88e-9036-415b-ad2c-2a5389999a95
 [047] + |   listen: unix/:(socket)
 [047] + |   replication_anon:
 [047] + |     count: 0
 [047] + |   replication:
 [047] + |     1:
 [047] + |       id: 1
 [047] + |       uuid: 6b413fa4-5dc0-4395-af5e-b02348f33390
 [047] + |       lsn: 6
 [047] + |       upstream:
 [047] + |         peer: test_user@unix/:/tarantool/test/var/047_replication/master.socket-iproto
 [047] + |         lag: 0.00026035308837891
 [047] + |         status: disconnected
 [047] + |         idle: 0.8051715195179
 [047] + |         message: timed out
 [047] + |         system_message: Connection timed out
 [047] + |     2:
 [047] + |       id: 2
 [047] + |       uuid: f990adde-8807-4921-942c-143717974b42
 [047] + |       lsn: 0
 [047] + |   signature: 6
 [047] + |   status: running
 [047] + |   vclock: {1: 6}
 [047] + |   uptime: 3
 [047] + |   lsn: 0
 [047] + |   sql: []
 [047] + |   gc: []
 [047] + |   vinyl: []
 [047] + |   memory: []
 [047] + |   pid: 2585
 [047]   | ...

Steps to reproduce:

Optional (but very desirable):

• coredump
• backtrace
• netstat