osc: stores downloaded (supposed) RPM in network-controlled filesystem paths

A External Control of File Name or Path vulnerability in osc of SUSE Linux Enterprise Module for Development Tools 15, SUSE Linux Enterprise Software Development Kit 12-SP5, SUSE Linux Enterprise Software Development Kit 12-SP4; openSUSE Leap 15.1, openSUSE Factory allowed remote attackers that can change downloaded packages to overwrite arbitrary files. This issue affects: SUSE Linux Enterprise Module for Development Tools 15 osc versions prior to 0.169.1-3.20.1. SUSE Linux Enterprise Software Development Kit 12-SP5 osc versions prior to 0.162.1-15.9.1. SUSE Linux Enterprise Software Development Kit 12-SP4 osc versions prior to 0.162.1-15.9.1. openSUSE Leap 15.1 osc versions prior to 0.169.1-lp151.2.15.1. openSUSE Factory osc versions prior to 0.169.0 .