server ssh UPDATE authentication with ECDSA keys

ECDSA keys can now be used both as a hostkey and for client
authentication. Three key pairs added for a new test.
diff --git a/tests/data/id_ecdsa384.pub b/tests/data/id_ecdsa384.pub
new file mode 100644
index 0000000..5dbf598
--- /dev/null
+++ b/tests/data/id_ecdsa384.pub
@@ -0,0 +1 @@
+ecdsa-sha2-nistp384 AAAAE2VjZHNhLXNoYTItbmlzdHAzODQAAAAIbmlzdHAzODQAAABhBBLPUkUBaICa0rBZLIJd1lTA1NL+b5wKmJQ8Le8dnzZLWDaKFtCk3ggAgAB9FMRH6udXn+oKUOYKMGw5IhrDzpVwjKTACpw3LTHSK8ajJ+lUvj/0Jl9VJ/+HAhPF9sIrkw== test@libnetconf2