Instead of using ~/Downloads, which we have no control over (OK for
the CI, but not locally), create a parent temp dir, then another temp
dir inside it.
Also rename it to nestedTempDirs, the issue from the bug report wasn't
tested because it relied on a dir being created, then failing to set
permissions on it. The code has changed a lot since then.
Pick-to: 6.7 6.6 6.5 6.2
Change-Id: I2b03d5d761117aaf436041c13c0dc394b106bf89
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
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