virnetdevbandwidth: Don't generate burst outside of boundaries

virnetdevbandwidth: Don't generate burst outside of boundaries

When generating TC rules for domain's outbound traffic, Libvirt
will use the 'average' as the default for 'burst' - it's been
this way since the feature introduction in v0.9.4-rc1~22. The
reason is that 'average' considers 'burst' for policing. However,
when parsing its command line TC uses an unsigned int (with
overflow detection) to store the 'burst' size. This means, that
the upper limit for the value is UINT_MAX, well UINT_MAX / 1024
because we are putting the value in KiB onto the command line.

Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1912210
Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Laine Stump <laine@redhat.com>