Incompatible with LSP installed by LspInstall

https://github.com/kabouzeid/nvim-lspinstall is a convenient plugin to install LSP servers. They end up in a separate directory outside of `$PATH` (`~/.local/share/nvim/lspinstall/python/./node_modules/.bin/pyright-langserver` in my case), but https://github.com/kabouzeid/nvim-lspinstall/blob/54b439241e83e0a9ce8f6bcdf3b2c560a2328792/lua/lspinstall.lua#L94 corrects the default `cmd` for `lspconfig` to point to that location. However `py_lsp` doesn't pick up on it for some reason, perhaps overriding `cmd` or `cmd_cwd` in `default_config`?

This is with `py_lsp` installed and used to set up Pyright:

And this is with `py_lsp` disabled: (note `cmd`)