loginctl: improve print_{session|user|seat}_status_info() functions

loginctl: improve print_{session|user|seat}_status_info() functions

1) Instead of checking if we need to print a new line on each iteration,
pass the "new_line" as a pointer to those functions, so they can use
it to check if a new line is needed. This makes the code more consistent
as it is done in other places: machinectl, systemctl...

2) Move the error messages from show_{session|user|seat}() to their
appropriate print_{session|user|seat}_status_info() functions, this will
prevent from logging an error message twice in case show_properties()
fails and it will improve code readability.

3) Also do not ignore error codes on these functions.