gsocket: Fix SO_NOSIGPIPE regression on Darwin
Where the early call to g_socket_set_option() fails because of
check_socket() failing due to inited still being FALSE.
This brings 634b6921 back into working order, by fixing the regression introduced in 39f047e8 (/cc @pwithnall).
Co-authored-by: Ole André Vadla Ravnås oleavr@gmail.com