Fix re-installation via package uri-s

It is allowed to install a package via a "package" URI. This means that
if a package with the same name is already installed (for any user), please
(re-)install it for the current user.

This was broken as mPackageURI.getPath() does not work for such package
URIs. This call is only needed when we need to show UI, but for package
URIs we don't even new UI, hence we can move it for the "content" path.

Test: atest CtsPackageInstallTestCases
Bug: 117768093
Change-Id: I58d3abde22ae0a77aabe5068680fd0148d799776