FIX: improve postgres upgrade reliability (#989)

On some systems the /shared/postgres_data directory might be a mount
point, so in order to avoid failure in this scenario, move the postgres
data files directly instead of manipulating the data directory.

see https://meta.discourse.org/t/infinite-loop-during-postgres-upgrade/91767/8?u=lavamind

Author: jcharaoui

templates/postgres.15.template.yml

@@ -132,8 +132,10 @@ run:
            exit 1
          fi
 
-         mv /shared/postgres_data /shared/postgres_data_old
-         mv /shared/postgres_data_new /shared/postgres_data
+         mkdir /shared/postgres_data_old
+         mv /shared/postgres_data/* /shared/postgres_data_old
+         mv /shared/postgres_data_new/* /shared/postgres_data
+         rmdir /shared/postgres_data_new
 
          echo -------------------------------------------------------------------------------------
          echo UPGRADE OF POSTGRES COMPLETE

templates/postgres.template.yml

@@ -139,8 +139,10 @@ run:
            exit 1
          fi
 
-         mv /shared/postgres_data /shared/postgres_data_old
-         mv /shared/postgres_data_new /shared/postgres_data
+         mkdir /shared/postgres_data_old
+         mv /shared/postgres_data/* /shared/postgres_data_old
+         mv /shared/postgres_data_new/* /shared/postgres_data
+         rmdir /shared/postgres_data_new
 
          echo -------------------------------------------------------------------------------------
          echo UPGRADE OF POSTGRES COMPLETE