Tests: skip ssl_cache.t server certificate verify if not supported.

Without X509_V_FLAG_PARTIAL appeared in OpenSSL 1.0.2 and supported
by Net::SSLeay (1.83+), it is not possible to use leaf certificates
in the trust store as full trust anchors.

Author: pluknet

ssl_cache.t

@@ -184,6 +184,9 @@ like(http_get('/t'), qr/200 OK.*SUCCESS:.*1\.example\.com/s, 'proxy ssl');
 sub get {
 	my ($port, $ca, $cert) = @_;
 
+	$ca = undef if $IO::Socket::SSL::VERSION < 2.062
+		|| !eval { Net::SSLeay::X509_V_FLAG_PARTIAL_CHAIN() };
+
 	http_get('/t',
 		PeerAddr => '127.0.0.1:' . port($port),
 		SSL => 1,