util: don't return early from virNetDevTapReattachBridge() if "force" is true

util: don't return early from virNetDevTapReattachBridge() if "force" is true

It can be useful to force an interface to be detached/reattached from
its bridge even if it's the same bridge - possibly something like the
virtualport profileID has changed, and a detach/attach cycle will get
it connected with the new profileID.

The one and only current use of virNetDevTapReattachBridge() sets
force to false, to preserve current behavior. An upcoming patch will
use it with force set to true.

Signed-off-by: Laine Stump <laine@redhat.com>
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>