registry: add tests for unresolvable domain names in isSecure

Signed-off-by: Tibor Vass <teabee89@gmail.com>

registry/registry_test.go

@@ -348,6 +348,9 @@ func TestIsSecure(t *testing.T) {
 		{"example.com:5000", []string{"42.42.42.42/8"}, false},
 		{"127.0.0.1:5000", []string{"127.0.0.0/8"}, false},
 		{"42.42.42.42:5000", []string{"42.1.1.1/8"}, false},
+		{"invalid.domain.com", []string{"42.42.0.0/16"}, true},
+		{"invalid.domain.com", []string{"invalid.domain.com"}, false},
+		{"invalid.domain.com:5000", []string{"invalid.domain.com"}, false},
 	}
 	for _, tt := range tests {
 		// TODO: remove this once we remove localhost insecure by default