Resilient watches

Got some help in #coreos to find out what to do about 401 errors. Turns out the answer is to restart the watch with a fresh Get. That ensures metafora will never miss events.

The diff looks like an absolute mess. Basically all I did was put *another* for loop around the initial Get when we start watching, and have 401s continue that outer loop.


bleh
My fault but this is actually just the default value and it can be overridden.   See https://github.com/lytics/metafora/blob/resilient-watches/m_etcd/coordinator.go#L216 

I guess we should rename it to DefaultClaimTTL...