Reading and writing container config from /etc/pve/lxc/ can hang
indefinitely if the Proxmox cluster filesystem (pmxcfs) is slow or
unresponsive. This causes the installer to appear to hang after
"Configuring socket bind mount..." with no further output.
Add 10-second timeouts to both cp operations and provide helpful error
messages suggesting the user check cluster health with 'pvecm status'.
Related to #738
b3b8081426