use unescape instead of escape for the cpio files

[larssp]

This is a possible solution to #161

Example: Building "Cbc"

downloaded files to the cache are:

• noarch%2Fmingw64-Cbc-2.9.2-1.19.noarch.rpm
• noarch%2Fmingw64-Clp-1.16.3-1.21.noarch.rpm
• noarch%2Fmingw64-libCgl1-0.59.2-3.20.noarch.rpm
• noarch%2Fmingw64-libCoinUtils3-2.10.3-2.21.noarch.rpm
• noarch%2Fmingw64-libstdc%2B%2B6-8.2.0-2.1.noarch.rpm
• noarch%2Fmingw64-libwinpthread1-5.0.3-1.13.noarch.rpm
• noarch%2Fmingw64-Osi-0.107.2-2.21.noarch.rpm
• repodata%2F6c3cf735 ... b38cb-primary.xml
• repodata%2Frepomd.xml

7z extracts noarch%2Fmingw64-libstdc%2B%2B6-8.2.0-2.1.noarch.rpm
to mingw64-libstdc++6-8.2.0-2.1.noarch.cpio

so the filename has to be unescaped, instead of escaped.

But I am not sure if the files should have escaped file names in the first place....
The escaped rpm file names are odd, because this was targeted by #141

[larssp]

Sorry, I just realized that there is PR #157 already targeting this issue.

[nalimilan]

So the problem is just that we needed unescape here instead of escape? Please comment on #157.