Update instructions for migrating postgres
Update instructions for migrating postgres

Include need for a maintenance window and how to migrate through
multiple versions of postgresql.

Change-Id: I9aad5450621bca1a91d7306d4cf9b5ab3fc71ab2

Linaro/lava-server,Linaro/lava-server,Linaro/lava-server,Linaro/lava-server