fix(xo-server/disconnectXenServer): delete pool association
fix(xo-server/disconnectXenServer): delete pool association

This should prevent the *server is already connected* issue after reinstalling host.

lmcro/xo-web,lmcro/xo-web,vatesfr/xo-web,lmcro/xo-web,vatesfr/xo-web