Enforce UpdateManager to avoid folders corruption

SUPNXP-9417 must be reproduced with a Nuxeo package to identify the cause and enforce the UpdateManager process.
Reproducing the customer case, I ended with a partially installed package:

• expanded JAR as a directory (where a JAR is expected, not a directory)
• no uninstall.xml file
• package is not installable and not uninstallable!

Issue is supposed to come from the successive calls to "remove", "import", "install", "restart" from the Admin Center.
I couldn't reproduce the issue with a 5.9.1 + nuxeo-dm package (only did a quick try).