Change the queries that check tuple counts on a particular segment,
in utility mode, to not print out the exact tuple counts, but a crude
classification of 0, 1, <5 or more tuples. That's less sensitive to how
the tuples are distributed across segments.

The locks_reindex test is moved to the regular regression suite. I rewrote
it to use a more advanced "locktest" view, copied from the
partition_locking test, which doesn't rely on utility mode.

These changes should make the tests work with even larger clusters,
but I've only tested with 1, 2, and 3 nodes.