Revert "ssh/tailssh: change to user directory when running login/command"

This reverts commit dc5bc32d8f.

It broke tests. (sadly, ones which we have disabled on CI, but go test
./ssh/tailssh broke)
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Internal Server Error - Gitea: Git with a cup of tea
500 Internal Server Error

Gitea Version: 1.28.0+dev-477-g8b6ad49a5f