alternator-test: another test for top-level attribute overwrite
alternator-test: another test for top-level attribute overwrite

Yet another test for overwriting a top-level attribute which contains
a nested document - here, overwriting it by just a string.

This test passes. In the current implementation we don't yet support
updates to specific attribute paths (e.g. a.b[3].c) but we do support
well writing and over-writing top-level attributes.

Signed-off-by: Nadav Har'El <625169824b719df98706d88646d0aae6f368ae4d@scylladb.com>

avikivity/scylla,avikivity/scylla,avikivity/scylla,scylladb/scylla,scylladb/scylla,scylladb/scylla,scylladb/scylla