plugins/bridge: clean masquerading rules
plugins/bridge: clean masquerading rules

In the Add command we set up masquerading rules that didn't have a
corresponding clean-up code in Del.

Add the clean-up code.

achanda/cni,squeed/plugins,squaremo/cni,mcastelino/cni,tomdee/cni,tangle329/cni,containernetworking/plugins,rosenhouse/cni,dcbw/cni,containernetworking/cni,containernetworking/plugins,dcbw/cni,squaremo/cni,achanda/cni,jonboulle/cni,appc/cni,steveeJ/cni,murat1985/cni,tangle329/cni,squeed/plugins,murat1985/cni,luxas/cni,rosenhouse/cni,luxas/cni,steveeJ/cni,tomdee/cni,kad/cni,mcastelino/cni,containernetworking/cni,jonboulle/cni,kad/cni,appc/cni