test: flaky replication/qsync_with_anon.test.lua test

[avtikhon]

Tarantool version:
Tarantool 2.5.0-250-ga9b99f0ef
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:
Got on OSX but should be on Linux too

Bug description:
https://gitlab.com/tarantool/tarantool/-/jobs/635602923#L3879
Issue:

[005] --- replication/qsync_with_anon.result	Mon Jul 13 02:05:20 2020
[005] +++ replication/qsync_with_anon.reject	Mon Jul 13 12:50:26 2020
[005] @@ -64,7 +64,7 @@
[005]   | ...
[005]  box.space.sync:insert{1} -- success
[005]   | ---
[005] - | - [1]
[005] + | - error: Quorum collection for a synchronous transaction is timed out
[005]   | ...
[005]  box.space.sync:insert{2} -- success
[005]   | ---
[005] @@ -80,8 +80,7 @@
[005]   | ...
[005]  box.space.sync:select{} -- 1, 2, 3
[005]   | ---
[005] - | - - [1]
[005] - |   - [2]
[005] + | - - [2]
[005]   |   - [3]
[005]   | ...
[005]  -- Testcase cleanup.
[005] 
[005] Last 15 lines of Tarantool Log file [Instance "master"][/tmp/tnt/005_replication/master.log]:
[005] 2020-07-13 12:50:25.878 [97248] main/254/console/unix/: I> set 'replication_synchro_timeout' configuration option to 5
[005] 2020-07-13 12:50:25.878 [97248] main/254/console/unix/: I> set 'replication_synchro_quorum' configuration option to 1
[005] 2020-07-13 12:50:26.347 [97248] main/223/main I> sending current read-view to replica at fd 35, aka unix/:/tmp/tnt/005_replication/master.socket-iproto,
[005] 2020-07-13 12:50:26.359 [97248] main/223/main I> read-view sent.
[005] 2020-07-13 12:50:26.393 [97248] main/223/main I> subscribed replica 2fb577db-49a0-41fa-b446-b1d6168cf005 at fd 35, aka unix/:/tmp/tnt/005_replication/master.socket-iproto,
[005] 2020-07-13 12:50:26.393 [97248] main/223/main I> remote vclock {1: 511} local vclock {0: 1003, 1: 511}
[005] 2020-07-13 12:50:26.394 [97248] relay/unix/:(socket)/101/main I> recover from `/tmp/tnt/005_replication/master/00000000000000001489.xlog'
[005] 2020-07-13 12:50:26.419 [97248] main/280/console/unix/: I> set 'replication_synchro_timeout' configuration option to 0.1
[005] 2020-07-13 12:50:26.433 [97248] main/280/console/unix/: I> set 'replication_synchro_quorum' configuration option to 2
[005] 2020-07-13 12:50:26.675 [97248] main/290/console/unix/: I> set 'replication_synchro_quorum' configuration option to 3
[005] 2020-07-13 12:50:26.812 [97248] main/300/console/unix/: I> set 'replication_synchro_quorum' configuration option to 2
[005] 2020-07-13 12:50:26.845 [97248] relay/unix/:(socket)/101/main coio.cc:379 !> SystemError unexpected EOF when reading from socket, called on fd 35, aka unix/:/tmp/tnt/005_replication/master.socket-iproto: Broken pipe
[005] 2020-07-13 12:50:26.845 [97248] relay/unix/:(socket)/101/main C> exiting the relay loop
[005] 2020-07-13 12:50:26.933 [97248] main/304/console/unix/: I> set 'replication_synchro_timeout' configuration option to 5
[005] 2020-07-13 12:50:26.933 [97248] main/304/console/unix/: I> set 'replication_synchro_quorum' configuration option to 1

Steps to reproduce:

Optional (but very desirable):

• coredump
• backtrace
• netstat