Fix occasional test failure.

The WebSocketClient first read headers via
a BufferedReader, then tried to read the body
via the underlying InputStream. Depending on
the structure of the incoming packets reading
the body failed because some bytes were already
buffered in the reader and no longer available
by the stream. The switch between rader and stream
was motivated, because the decoding also had to
switch from ISO-8859-1 (headers) to UTF-8 (body).

We now simulate a rudimentary reader which always
reads from the stream and allows to change the
decoding charset while reading.


git-svn-id: https://svn.apache.org/repos/asf/tomcat/tc7.0.x/trunk@1551729 13f79535-47bb-0310-9956-ffa450edef68