Fix imports in _hdfs_test

There is no such thing as unittes2 right? I mean the code always threw ...
Rename fail_if_exists to raise_if_exists

I'm not sold myself that adding the decorator is the cleanest way. Some
static analyzers will go wild, but you have to live with that when
using such dynamic programming languages.
Add default / configurable rpc connect timeout

Without this timeout, it was possible for rpc connections
(for example, reporting that a task was done) to hang forever
Merge pull request #398 from danielhfrank/rpc-connect-timeout

Add default / configurable rpc connect timeout
Merge pull request #397 from Tarrasch/raise-if-exists

Rename fail_if_exists to raise_if_exists
Merge pull request #394 from spotify/arash/clean-hdfs-test

Fix imports in _hdfs_test
Equality operator for Task
Merge pull request #400 from Houzz/eq_op

Adds equality operator to Task
Make S3Target respect format