Remove dry-run mode from isolationtester
Remove dry-run mode from isolationtester

The original purpose of the dry-run mode is to be able to print all the
possible permutations from a spec file, but it has become less useful
since isolation tests has improved regarding deadlock detection as one
step not wanted by the author could block indefinitely now (originally
the step blocked would have been detected rather quickly).  Per
discussion, let's remove it.

Author: Michael Paquier
Reviewed-by: Asim Praveen, Melanie Plageman
Discussion: 3db7b5c43d4c51623ac3eab04fc43183999b0489@paquier.xyz
(cherry picked from commit 9903338b5ea59093d77cfe50ec0b1c22d4a7d843)

lisakowen/gpdb,greenplum-db/gpdb,xinzweb/gpdb,xinzweb/gpdb,xinzweb/gpdb,xinzweb/gpdb,lisakowen/gpdb,greenplum-db/gpdb,greenplum-db/gpdb,xinzweb/gpdb,lisakowen/gpdb,50wu/gpdb,greenplum-db/gpdb,xinzweb/gpdb,greenplum-db/gpdb,50wu/gpdb,50wu/gpdb,lisakowen/gpdb,xinzweb/gpdb,lisakowen/gpdb,xinzweb/gpdb,50wu/gpdb,greenplum-db/gpdb,50wu/gpdb,lisakowen/gpdb,greenplum-db/gpdb,lisakowen/gpdb,50wu/gpdb,50wu/gpdb,lisakowen/gpdb,50wu/gpdb,greenplum-db/gpdb