Uncaught exception when deleting larger box

[SH]

User reported:

Uncaught PHP Exception Symfony\Component\Filesystem\Exception\IOException: "Failed to remove directory "/data/domains/domain.cz/roman/Maildir": rmdir(/data/domains/domain.cz/roman/Maildir): Directory not empty." at /opt/admin/vendor/symfony/symfony/src/Symfony/Component/Filesystem/Filesystem.php line 180 {"exception":"[object] (Symfony\Component\Filesystem\Exception\IOException(code: 0): Failed to remove directory \"/data/domains/domain.cz/roman/Maildir\": rmdir(/data/domains/domain.cz/roman/Maildir): Directory not empty. at /opt/admin/vendor/symfony/symfony/src/Symfony/Component/Filesystem/Filesystem.php:180)"} []

[SH]

fix #395 use faster system rm as background process

→ <<cset 5bfab05979b1>>