Does not normalise file ownerships in .epub files

This bug was originally reported by Holger Levsen (holger@debian.org, @holger) in Debian bug #920732:

debian-edu-doc version 2.10.11 when tested on tests.r-b.o shows:

│ │ │ ├── ./usr/share/doc/debian-edu-doc-da/debian-edu-buster-manual.epub
│ │ │ │ ├── bsdtar -tvf {}
│ │ │ │ │ @@ -1,87 +1,87 @@
│ │ │ │ │  drwxr-xr-x  0 0      0           0 Feb 28 16:03 epub/
│ │ │ │ │  drwxr-xr-x  0 0      0           0 Feb 28 16:03 epub/META-INF/
│ │ │ │ │ --rw-r--r--  0 1111   1111      255 Jan  1  1970 epub/META-INF/container.xml
│ │ │ │ │ +-rw-r--r--  0 2222   2222      255 Jan  1  1970 epub/META-INF/container.xml
│ │ │ │ │  drwxr-xr-x  0 0      0           0 Feb 28 16:03 epub/OEBPS/
│ │ │ │ │ --rw-r--r--  0 1111   1111     2935 Jan  1  1970 epub/OEBPS/ar01s02.html
│ │ │ │ │ --rw-r--r--  0 1111   1111    19969 Jan  1  1970 epub/OEBPS/ar01s03.html
│ │ │ │ │ +-rw-r--r--  0 2222   2222     2935 Jan  1  1970 epub/OEBPS/ar01s02.html
│ │ │ │ │ +-rw-r--r--  0 2222   2222    19969 Jan  1  1970 epub/OEBPS/ar01s03.html