client: change anyhow Error display representation

client: change anyhow Error display representation

Improve error message output by showing the full Error context, using
the alternate selector '{:#}" [0].
Without this, only the outermost context is displayed, which in case
of pxar extraction errors is mostly not enough to find the underlying
issue.

[0] https://docs.rs/anyhow/1.0.69/anyhow/struct.Error.html#display-representations

Signed-off-by: Christian Ebner <c.ebner@proxmox.com>