In websockify v0.9.0, the 'socket' staticmethod moved from the
websockfiy.websocket.WebSocketServer class to the
websockify.websockifyserver.WebSockifyServer class [1][2], so our
import of the top-level module is no longer sufficient for accessing
the 'socket' method [3] when using v0.9.0:
AttributeError: module 'websockify' has no attribute 'WebSocketServer'
This adds a try_import from the v0.9.0 location and uses
WebSockifyServer.socket if the module is present. Otherwise, it
will fall back on the old location. This way, we are able to run with
websockify v0.9.0 and earlier versions with the same code.
Partial-Bug: #1840788
[1] 8a69762249
[2] e47591f4aa
[3] https://github.com/novnc/websockify/blob/v0.9.0/websockify/__init__.py
Change-Id: I4a50e2f772101315140df43910be2e3f69a63b73
791fa595e6