Use <substeps> in pg_upgrade's procedure
Use <substeps> in pg_upgrade's procedure

For clarity, so that the substeps are not numbered identically to the
outer procedure's steps.

Per report from Andy Colson in
http:20d3a40ced6be2fb65133595b6f7468cf90bb21b@squeakycode.net

zeroae/postgres-xl,zeroae/postgres-xl,zeroae/postgres-xl,zeroae/postgres-xl,zeroae/postgres-xl