NSFS | NC | Avoid vacuumAndAnalyze on nc nsfs without db

[romayalon]

Explain the changes

1. Avoid vacuumAndAnalyze call on nc nsfs without db environment. (more places like sts_rest and namespace_montior calling system_store)

Issues: Fixed #xxx / Gap #xxx

1. will fix Noobaa_nsfs service restarts due to panic on 2 of the protocol nodes #7735
2. make sts_rest and namespace_monitor work on nc nsfs without db.

Testing Instructions:

1. manually change postgres_client.PostgresTable.constructor setInterval(this.vacuumAndAnalyze, 86400000, this).unref(); to setInterval(this.vacuumAndAnalyze, 1, this).unref();
2. sudo node src/cmd/nsfs.js

• Doc added/updated
• Tests added