db: bail on a prune operation if both trees have a prefix
db: bail on a prune operation if both trees have a prefix

If both trees have prefixes that don't match, bail on the prune
operation.

Signed-off-by: Paul Moore <a027184a55211cd23e3f3094f1fdc728df5e0500@paul-moore.com>

seccomp/libseccomp,seccomp/libseccomp,seccomp/libseccomp