Rc0 release broke dockerfile for windows support

[timliubentoml]

Describe the bug

From support channel in slack https://bentoml.slack.com/archives/CKRANBHPH/p1654618223220669

User mentions that windows support was working with a7 but not rc0.

It seems to be a path issue within the generated dockerfile (path with "\" and "/" raise an error), for example line 118 this command raises an error RUN chmod +x /home/bentoml/bento\env\docker\entrypoint.sh

Docker file contains slashes which are not compatible with windows

To Reproduce

Expected behavior

Screenshots/Logs

Environment:

• OS: [e.g. MacOS 10.14.3]
• Python Version [e.g. Python 3.7.1]
• BentoML Version [e.g. BentoML-0.8.6]

Additional context

[aarnphm]

2547 will fix this