Fix failover script to use absolute path to the database cluster.

Otherwise failover doesn't work when startall is executed from other
than in the directory where pgpool_setup starts.
Reorganize port numbers assigned in pgool_setup.

Assign base port (11000 by default) to pgpool, base port + 1 to pcp,
port + 2 to PostgreSQL node0, port + 3 to PostgreSQL node1 and so on.
This assigns fixed port numbers to pgpool and pcp port, which makes
pgpool_setup user's life a little bit easier, because they don't need
to check README.port to make sure the pgpool and pcp port any more.

Some of regression tests uses immediate numeric port numbers and
adjusted to meet the change.
Fixing [pgpool-hackers: 694] pgpool-II 3.4 can't cancel query
pool_write_noerror() returns 0 when successful, But pool_write_and_flush_noerror()
function was assuming otherwise. Correcting the wrong IF statement in the function.
Merge branch 'pgpool2'