This has the next wave of RTT integration with the router and also
factors some common RTT-related helpers out to lib. While we were
in here we also got rid of the coordinate disable config so we don't
need to deal with the complexity in the router (there was never a
user-visible way to disable coordinates).
While I'm at it, add a DurationMinusBufferDomain() function to calculate the min/max for a given call to DurationMinusBuffer() in order to keep the implementation details self-contained.
used to schedule a TTL check. e.g.
d := lib.DurationMinusBuffer(60 * time.Duration, 10 * time.Second, 16)
will return a duration between 46.875s and 50s.
Consolidate code duplication and tests into a single lib package. Most of these functions were from various **/util.go functions that couldn't be imported due to cyclic imports. The consul/lib package is intended to be a terminal node in an import DAG and a place to stash various consul-only helper functions. Pulled in hashicorp/go-uuid instead of consolidating UUID access.
