zebra: Allow tunneldump data to work properly on non-supported kernels

zebra: Allow tunneldump data to work properly on non-supported kernels

When zebra requests tunnel data it is sending a RTM_GETTUNNEL per
interface that is a VXLAN tunnel.  If the kernel that is being
used does not support the particular request type then zebra
will get a error message per tunnel request back.  Unfortunately
netlink_parse_info *stops* reading on the first error message.
Therefor one kernels that are returning an error message
let's gather all of those errors.  This will allow things
like route reads to actually work properly

Fixes: #12056
Signed-off-by: Donald Sharp <sharpd@nvidia.com>