test: vinyl/errinj flaky fails on high loaded host on box.snapshot()

[avtikhon]

Tarantool version:
master
OS version:
Ubuntu 18.04

Bug description:
Failed:

[016] --- vinyl/errinj.result	Mon Jul 15 07:18:57 2019
[016] +++ vinyl/errinj.reject	Mon Jul 15 17:00:21 2019
[016] @@ -86,7 +86,7 @@
[016]  ...
[016]  box.snapshot();
[016]  ---
[016] -- ok
[016] +- error: Error injection 'vinyl dump'
[016]  ...
[016]  num_rows = num_rows + range();
[016]  ---

[009] --- vinyl/errinj.result	Mon Jul 15 07:18:57 2019
[009] +++ vinyl/errinj.reject	Mon Jul 15 17:26:04 2019
[009] @@ -352,7 +352,7 @@
[009]  ...
[009]  box.snapshot();
[009]  ---
[009] -- ok
[009] +- error: Error injection 'xlog write injection'
[009]  ...
[009]  #s:select({1})
[009]  ---

All the fails are common and have the following structure:

-- enabling the error injection
errinj.set("ERRINJ_VY_RUN_WRITE", true);
num_rows = num_rows + range();
-- fails due to error injection
box.snapshot();

-- disabling the error injection
errinj.set("ERRINJ_VY_RUN_WRITE", false);
fiber.sleep(0.06);
num_rows = num_rows + range();
-- FAILS HERE: still fails at the error injection, but in real should pass
box.snapshot();

Steps to reproduce:

l=0 ; while time ./test-run.py -j15 `for r in {1..15} ; do echo vinyl ; done` 2>/dev/null ; do l=$(($l+1)) ; echo ======== $l ============= ; done

l=0 ; while time ./test-run.py -j10 `for r in {1..150} ; do echo vinyl/errinj.test.lua ; done` 2>/dev/null ; do l=$(($l+1)) ; echo ======== $l ============= ; done

Optional (but very desirable):

• coredump
• backtrace
• netstat

[avtikhon]

At the 2.4.0-16-gcdf502c66 version the issue was not reproduced, but got the following error:

--- vinyl/errinj.result	Fri Jan 17 13:19:04 2020
+++ var/005_vinyl/errinj.result	Wed Jan 22 12:40:36 2020
@@ -963,7 +963,7 @@
 ...
 box.snapshot()
 ---
-- ok
+- error: 'Invalid VYLOG file: Slice 1079 deleted but not registered'
 ...
 -- Create another run file. This will trigger compaction
 -- as run_count_per_level is set to 1. Due to the error

[avtikhon]

The shown issues above happened because of 3 other issues:

#126
tarantool/test-run#261
tarantool/tarantool#5436