openssl/ssl/context: test that we are refcounting correctly

Not a perfect test, on failure it _might_ exit with this output:

Process didn't exit successfully:
`/home/cody/g/rust-openssl/openssl/target/debug/openssl-8e712036e3aac4fe`
(signal: 11)

But unclear if we can do any better.

openssl/src/ssl/tests/mod.rs

@@ -1045,3 +1045,16 @@ fn flush_panic() {
     let mut stream = SslStream::connect(&ctx, stream).unwrap();
     let _ = stream.flush();
 }
+
+#[test]
+fn refcount_ssl_context() {
+    let ssl = {
+        let ctx = SslContext::new(SslMethod::Sslv23).unwrap();
+        ssl::Ssl::new(&ctx).unwrap()
+    };
+
+    {
+        let new_ctx_a = SslContext::new(SslMethod::Sslv23).unwrap();
+        let _new_ctx_b = ssl.set_ssl_context(&new_ctx_a);
+    }
+}