[webapp] webapp ssh, remove password prompt

[patricklee2]

work in progress

Strange characters appear when I type in the ssh session.

root@patle-build:/home/patle/azure-cli# az webapp ssh -g patle-test -n patle-test
Auto-selecting port: 45027
SSH is available ( username: root, password: Docker! )
Websocket tracing disabled, use --verbose flag to enable
Successfully connected to local server..
  _____
  /  _  \ __________ _________   ____
 /  /_\  \___   /  |  \_  __ \_/ __ \
/    |    \/    /|  |  /|  | \/\  ___/
\____|__  /_____ \____/ |__|    \___  >
        \/      \/                  \/
A P P   S E R V I C E   O N   L I N U X

Documentation: http://aka.ms/webapp-linux
NodeJS quickstart: https://aka.ms/node-qs

c9763f59784d:~# [63;17Rs^C
c9763f59784d:~#

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[patricklee2]

closed in favour of #8324