service: page-server: return port back to user, v2

Signed-off-by: Ruslan Kuprieiev <kupruser@gmail.com>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
service: page-server: allow requesting page-server without setting any ps_info

Since we now can return port to user in autobind case, it's ok to request
page-server without setting ps_info.

Signed-off-by: Ruslan Kuprieiev <kupruser@gmail.com>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
test: rpc: test page-server

Signed-off-by: Ruslan Kuprieiev <kupruser@gmail.com>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>