* cassandra2: default connection_timeout_millisecond so env-var configs keep the 600ms timeout
The scaffold documents a 600ms default, but the value has no SetDefault. A
config supplied purely through env vars (or a minimal toml) that omits the
key read back 0, silently overriding the client timeout with no bound.
* ydb: default the table path prefix so env-var configs keep the seaweedfs sub-path
The scaffold documents prefix = "seaweedfs", but with no SetDefault a config
that omits it lands tables at the database root instead of under seaweedfs/.
Chris Lu
39ff5ae767