test:cover reloadLogs twice in fork mode with /dev/null log path

[belte42]

Q	A
Bug fix?	no
New feature?	no
BC breaks?	no
Deprecations?	no
Tests pass?	yes
Fixed tickets	Unitech/pm2#5509
License	MIT
Doc PR	n/a

Nice seeing that the reloadLogs issue has been fixed in the development branch already!

This PR adds a regression test for Unitech/pm2#5509 to test/e2e/logs/log-reload.sh.

In fork mode, pm2 reloadLogs worked the first time, then failed on every later call when a log path was /dev/null or NULL:

TypeError: Cannot read properties of undefined (reading '_file')

The real log files were never reopened, so PM2 kept writing to the rotated files. With logrotate, the logs grew without limit. This still happens on the latest (7.0.4) release

development already fixes it in StdioLogger.close (the if (stds[k] && stds[k]._file) guard). There is no test for it yet, so this adds one to keep it fixed.

Test

Fork mode, -o /dev/null -e err-rel.log. The test deletes the error log, runs reloadLogs, checks the log is recreated, then does the same a second time.

• On master / 7.0.4: the second check fails.
• On development: all checks pass.

[CLAassistant]

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