logind: use session_get_state() to get sessions state of the user

logind: use session_get_state() to get sessions state of the user

In function user_get_state() remove the session_is_active() check, just
count on the session_get_state() function to get the correct session
state.

session_is_active() may return true before starting the session scope
and user service, this means it will return true even before the creation
of the session fifo_fd which will produce incorrect states.

So be consistent and just use session_get_state().