Test Failure on S390x architecture in fedora koji

The test bus::vtable::vtable_bitfield failed repeatedly on fedora koji for s390x architecture.
https://kojipkgs.fedoraproject.org//work/tasks/8160/66828160/build.log

The result doesn't coresspond by a small margin.

---- bus::vtable::vtable_bitfield stdout ----
thread 'bus::vtable::vtable_bitfield' panicked at 'assertion failed: (left == right)
left: 12307456,
right: 12307643', src/bus/vtable.rs:90:5

[codyps]

hmmm... that bitfield handling code we have is kind of funky. https://github.com/jmesmon/rust-systemd/blob/e9c4ddb3f901026d9ccdc8de1247ab5c3cf048a3/libsystemd-sys/src/bus/vtable.rs#L48-L81

Very possible we're just not handling big endian bitfields properly. Might make sense just to switch to some library that can get this right for us.

[sharkcz]

Please let me (sharkcz [at] fedoraproject.org) know if you would need an access to a s390x system to further debug this issue.