Trace the calls to DeletePiecesService.DeletePieces method and add
metrics for having statistics about the rate that specific storage node
is dialed and duration time spent on dialing storage nodes.
These statistics will help us to find out if we should implement
connections queues to storage node for reducing the deletion time in cae
that we see that we're spending too much time dialing frequent storage
nodes.
Ticket: https://storjlabs.atlassian.net/browse/SM-85
Change-Id: I9601676c3a8ad96c73c93833145929e4817755e2
Create a service for deleting pieces of storage nodes.
Currently the DeletePieces method returns after a success threshold,
completion or a timeout.
The end goal is to return when reaching the success threshold and
leaving the remaining goroutines running after DeletePieces method
returns and add a life cycle to the service that it waits for them when
it closes.
This is the first commit for ticket:
https://storjlabs.atlassian.net/browse/V3-3476
Change-Id: If740bbf57c741f880449980b8176b036dd956c7b
