content-dirs check: silently skip paths that cannot be resolved

content-dirs check: silently skip paths that cannot be resolved

Since commit 8e623a2930f7aee4b3309b1f297613a250ee4698, the inequality
check for content-dirs prints a warning if a content directory path
could not be resolved, i.e., if `abs_path` returns undef. Among other
things, `abs_path` returns undef if the path has an inner (= any but
last) component that does not exist. This can happen for a storage
with content type `iso,vztmpl` and `create-subdirs` set to 0, in case
`template/` does not exist. In this case, the warnings printed by
pvestatd are quite noisy.

As missing content directories are not a problem per se, remove the
warning and just ignore the directory during the inequality check.

Signed-off-by: Friedrich Weber <f.weber@proxmox.com>