log invalid owners to system log, and continue with next group just as
if permission checks fail for the following operations:
- verify store with limited permissions
- list store groups
- list store snapshots
all other call sites either handle it correctly already (sync/pull), or
operate on a single group/snapshot and can bubble up the error.
Signed-off-by: Fabian Grünbichler <f.gruenbichler@proxmox.com>
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