selftest: net: fix typo in altname test

selftest: net: fix typo in altname test

commit 1b704b27beb11ce147d64b21c914e57afbfb5656 upstream.

If altname deletion of the short alternative name fails, the error
message printed is: "Failed to add short alternative name".
This is obviously a typo, as we are testing altname deletion.

Fix this using a proper error message.

Fixes: f95e6c9c4617 ("selftest: net: add alternative names test")
Signed-off-by: Andrea Claudi <aclaudi@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>