db: Modify upgrade cmd to migrate database from Postgres to Sqlite

[harishsurf]

This is part 2 of feat: Sqlite database migration work. Part one PR: #152

This change adds ansible tasks to ./mirror-registry upgrade cmd to migrate data from a running Postgres container to SQlite file based database which is mounted as a volume to Quay container. It also stores a backup of postgres data in {{ quay_root }}/quay-postgres-backup inside the host machine where the binary is run

[dmage]

@jonathankingfc can you take a look?

[harishsurf]

PR #157 replaces this