Rename 'json' and related variables to 'nodeNameJson'. Also rename the
test files along. This is a preparation for modifying how we detect node
names which will also require data from 'query-blockstats'.
Reviewed-by: NEric Blake <eblake@redhat.com>

Test cases named '1' and '2' differed only in the length of the backing
chain, so remove test case '2' and rename test '1' to 'basic'.
Reviewed-by: NEric Blake <eblake@redhat.com>

The code is rather magic so a test case will help making sure that
everything works well. The first case is a simple backing chain.