suppress false-negative error in templates and nvidia hook

suppress false-negative error in templates and nvidia hook

``/proc`` might be mounted with ``hidepid=2``.
This makes ``/proc/1/…`` appear absent for non-root users.
When using the templates or the nvidia hook as a non-root user
(e.g., when creating unprivileged containers) the error
"/proc/1/uid_map: No such file or directory" is printed.
Since the script works correctly despite the error, this error
message might be confusing for users.

Signed-off-by: Lukas Pirl <git@lukas-pirl.de>