So, this test fails on S390 because the actual test in
testBlockNodeNameDetect is dependent on the ordering of the entries in
the hash table, which is different on big endian machines.
There are two other tests which have multiple results in the backing
chain, 'same-backing' and 'relative', but their keys are reasonable
similar that we got lucky and the hashes are ordered the same.
I don't suspect that code that uses the tested function,
qemuBlockNodeNameGetBackingChain, is dependent on the ordering of keys
so this is actually only a problem in the test suite.
Sorry for the late notice for this.
Bjoern