tests: Fix error reporting on prlimit() call failure
tests: Fix error reporting on prlimit() call failure

prlimit() returns its error code in errno, not as a return value.

Signed-off-by: Philip Withnall <withnall@endlessm.com>

https://gitlab.gnome.org/GNOME/glib/issues/1044

endlessm/glib,endlessm/glib,endlessm/glib,endlessm/glib,endlessm/glib