default_role was ignored when query_parser_enabled was set to false, this was because update_pool_settings does not populate active_role field in query_router struct. The fix is simple, I just set it when the router is configured for the first time.

Note that as of this, what we say in docs:

### default_role
` ` ` 
path: pools.<pool_name>.default_role
default: "any"
` ` ` 

If the client doesn't specify, PgCat routes traffic to this role by default.
`any` round-robin between primary and replicas,
`replica` round-robin between replicas only without touching the primary,
`primary` all queries go to the primary unless otherwise specified.

is incorrect, because without the fix (and query_parser_enabled set to false), this is always treated as any (which touches the primary as well as the replicas).