Fix bug in JSONTokenApi plugin

[grz0]

Fixes:

handler exception: 'method' object is not subscriptable
exception
Traceback (most recent call last):
File "/root/websockify/websockify/websocket.py", line 910, in top_new_client
client = self.do_handshake(startsock, address)
File "/root/websockify/websockify/websocket.py", line 845, in do_handshake
self.RequestHandlerClass(retsock, address, self)
File "/root/websockify/websockify/websocket.py", line 114, in init
SimpleHTTPRequestHandler.init(self, req, addr, server)
File "/usr/lib/python3.4/socketserver.py", line 673, in init
self.handle()
Fixes:
File "/root/websockify/websockify/websocket.py", line 570, in handle
SimpleHTTPRequestHandler.handle(self)
File "/usr/lib/python3.4/http/server.py", line 398, in handle
self.handle_one_request()
File "/usr/lib/python3.4/http/server.py", line 386, in handle_one_request
method()
File "/root/websockify/websockify/websocket.py", line 536, in do_GET
if not self.handle_websocket():
File "/root/websockify/websockify/websocket.py", line 524, in handle_websocket
self.new_websocket_client()
File "/root/websockify/websockify/websocketproxy.py", line 48, in new_websocket_client
(self.server.target_host, self.server.target_port) = self.get_target(self.server.token_plugin, self.path)
File "/root/websockify/websockify/websocketproxy.py", line 103, in get_target
result_pair = target_plugin.lookup(token)
File "/root/websockify/websockify/token_plugins.py", line 72, in lookup
return self.process_result(resp)
File "/root/websockify/websockify/token_plugins.py", line 82, in process_result
return (resp.json['host'], resp.json['port'])
TypeError: 'method' object is not subscriptable

[DirectXMan12]

I don't think the calls to str() are necessary here.

[peprasetya]

On my test, I have error message:
handler exception: Int or String expected

When I change the line to:
return (str(resp.json['host']), str(resp.json['port']))

it solve the error. So on my case the str() is needed.
And the resp.json()[] is not work, so it should use just resp.json[].

My python is version 2.6.6

[DirectXMan12]

In general, LGTM 👍. Just one inline comment.