Allow command and connection retry configuration

When kazoo needs to retry commands or retry connections
there is a specific set of configuration that can be provided
to adjust these; allow that configuration to be passed to the
client configuration method.

Change-Id: I9c57e81ae3f82c7358ddabc7804a28fee7734c93
Add a helper tool which clears zookeeper test dirs

Create a tool that can clear any leftover garbage left
by the testing of taskflow unit tests with zookeeper for
when this is needed (for example, a test does not clean up
correctly on its own).

Change-Id: Icfaf28273b76a6ca27683d174f111fba2858f055
Fix spelling mistake

Fix usage of 'occurred' (misspelled).

Change-Id: Ie71814bc1cda6536578a3bec2e072863990b8efa
Default the impl_memory conf to none

This configuration isn't used for anything in the memory
backend so default it to none so that it doesn't need to
be provided (since it's not used).

Change-Id: I9e333aec52b697ebd3d5b1f4ec14d810e99bab19
Add a reset nodes function

Instead of using the retry subflow function to reset all
nodes, create a reset nodes function that will reset the
state of a given iterator of nodes to PENDING and then change
there desired intention to a provided intention.

Change-Id: Ia3f4fd4537e30a88d0d7b2271ca5be54832f724d
Merge "Add a helper tool which clears zookeeper test dirs"
Merge "Allow command and connection retry configuration"
Merge "Add a reset nodes function"
Merge "Default the impl_memory conf to none"
Don't create fake LogBook when we can not fetch one

When there is no LogBook nor backend in ZookeeperJob or something is
wrong with book data, we now return None from `book` property instead
of new (fake) LogBook. Having two (or more) logbooks with same uuid but
different data is too confusing and makes root cause of the problem
(backend or jobboard misconfiguration) less obvious.

This change also adds `book_name` and `book_uuid` properties to Job
abstract class to provide a way to access book data even if book
itself cannot be fetched.

Change-Id: Iae1f918e35d41794fc348860e6aa3b52ae2211f4