IFACE handling. Assume links are always good on nstartup (they almost always

IFACE handling. Assume links are always good on nstartup (they almost always

Simplify the handling of setting the links in the 10.interface eventscript
and remove the optimization to only call setifacelink on state change
to make the code simpler to read.

If a take ip event fails, flag the node as unhealthy.

Add a check to the interface script to check if the interface exists
or if it has been deleted.
So that we can capture and become UNHELTHY if someone deletes an interface
we are using to host public addresses.