Change pgbench to use the table names pgbench_accounts, pgbench_branches,

pgbench_history, and pgbench_tellers, rather than just accounts, branches,
history, and tellers.  This is to prevent accidental conflicts with real
application tables, as has been reported to happen at least once.  Also
remove the automatic "SET search_path = public" that it did at startup,
as this seems to restrict testing flexibility without actually buying much.
Per proposal by Joshua Drake and ensuing discussion.

Joshua Drake and Tom Lane