HttpsURLConnection fixes to pass URLConnectionTest and HttpsURLConnectionTest

    Add public getSecureSocket so that HttpsURLConnection can reset its sslSocket field on reused connections.

        luni/src/main/java/org/apache/harmony/luni/internal/net/www/protocol/http/HttpConnection.java

    discardIntermediateResponse now maintain old values for
    intermediateReponse, which is necessary when retrying the CONNECT
    method with proxy authorization.

        luni/src/main/java/org/apache/harmony/luni/internal/net/www/protocol/http/HttpURLConnectionImpl.java

    Clear sslSocket before retrying makeSslConnection to ensure we reconnect.
    makeSslConnection now resets sslSocket on resumed connection.
    makeSslConnection now exits early on existing connection.

        luni/src/main/java/org/apache/harmony/luni/internal/net/www/protocol/https/HttpsURLConnectionImpl.java

Change-Id: I6862a092e2584398f7aa1d2a8b66ad074775b6b3