Add a test for the UI API

The best way to test the UI interface is currently by using an openssl
command that uses password_callback.  The only one that does this is
'genrsa'.
Since password_callback uses a UI method derived from UI_OpenSSL(), it
ensures that one gets tested well enough as well.
Reviewed-by: NRich Salz <rsalz@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/2040)

test/recipes/03-test_ui.t

+#! /usr/bin/env perl
+# Copyright 2015-2016 The OpenSSL Project Authors. All Rights Reserved.
+#
+# Licensed under the OpenSSL license (the "License").  You may not use
+# this file except in compliance with the License.  You can obtain a copy
+# in the file LICENSE in the source distribution or at
+# https://www.openssl.org/source/license.html
+
+use strict;
+use warnings;
+use OpenSSL::Test;
+
+setup("test_ui");
+
+plan tests => 1;
+
+note <<"EOF";
+The best way to test the UI interface is currently by using an openssl
+command that uses password_callback.  The only one that does this is
+'genrsa'.
+Since password_callback uses a UI method derived from UI_OpenSSL(), it
+ensures that one gets tested well enough as well.
+EOF
+
+my $outfile = "rsa_$$.pem";
+ok(run(app(["openssl", "genrsa", "-passout", "pass:password", "-aes128",
+            "-out", $outfile])),
+   "Checking that genrsa with a password works properly");
+
+unlink $outfile;