parser: fix parser so that cache creation failure doesn't cause load failure
This is a minimal patch so that it can be backported to 2.11 and 2.10 which reverts the abort on error failure when the cache can not be created and write-cache is set.
This is meant as a temporary fix for https://bugzilla.suse.com/show_bug.cgi?id=1069906 https://bugzilla.opensuse.org/show_bug.cgi?id=1074429
where the cache location is being mounted readonly and the cache creation failure is causing policy to not be loaded. And the thrown parser error to cause issues for openQA.
Note: A cache failure warning will be reported after the policy load.
Signed-off-by: John Johansen john.johansen@canonical.com