With ucbhelper::Content now requiring an XComponentContext during construction,
calling "unopkg add" with an .oxt that requires license acceptance would lead to
an assertion about a null XComponentContext, as doChecksForAddExtension calls
the XPackage's checkPrerequisites -> checkLicnese -> getTextFromURL, which
creates an ucbhelper::Content with getMyBackend()->getComponentContext(), but
early release of the "tmp" manager would already have caused disposing of that
backend, which clears m_xComponentContext.

I assume this problem had always been lurking silently in the code.

Change-Id: I9f59c612fe3831b2f6dd832ef2f0505b6590b8e0