Docker with command shell=true should override entrypoint

Currently with the new CommandInfo there is a shell flag that if it's enabled, will wrap the command with /bin/sh -c with docker run.

However we don't override the entrypoint, therefore when a user specified a image with a entrypoint and also have shell=true then /bin/sh -c will become part of the argument to the entrypoint.

I don't think there is any example where users expect /bin/sh -c to be a argument in the entrypoint, and to make sure cases where shell is needed for expanding environment variables we also override the entrypoint.