Context key "extension.xar.packageconfiguration" is leaked when installing a XAR extension

When a XAR extension is installed, it seems that the context key "extension.xar.packageconfiguration" is being left over after the package installation.

The issue is that when you need to install programmatically multiple XAR extensions at once, the first installation will go through, but the second installation (and later ones) will fail as they will rely on the package configuration of the first extension, which is different from their package configuration.