Test has been changed such that sftp_limits() is called
when the limits@openssh.com extension is supported as well
as when it is not supported.
Also, a simple negative test has been added for NULL
argument.
Signed-off-by: Eshan Kelkar <eshankelkar@galorithm.com>
Reviewed-by: Jakub Jelen <jjelen@redhat.com>