Improve default network connectivity monintor: do not trigger network DOWN/UP...
Improve default network connectivity monintor: do not trigger network DOWN/UP if a default IP comes up or disapears whithout changing the connectivity state. Indeed, it was found that due to routers or OS bugs, sometimes IPv6 connectivity is unstable while IPv4 works perfectly, causing frequent reINVITEs during calls due to the previous network connectivity monitor policy.