use a common function between collection_jitter and flush_jitter. which
creates the same behavior between the two options.
going forward, both jitters will be random sleeps that get re-evaluated
at runtime for every interval (previously only collection_jitter did
this)
also fixes behavior so that both jitters will exit in the event of a
process exit.
closes#1296
This will basically make the root directory a place for storing the
major telegraf interfaces, which will make telegraf's godoc looks quite
a bit nicer. And make it easier for contributors to lookup the few data
types that they actually care about.
closes#564