Initial Impala failure testing library + modularize run-workload

This adds initial changes for the Impala failure testing library. It also refactors
run workload into its own module to it can be used in other tests.

The failure testing has two main components - the first is an object model on top on top
of Impala services in a cluster. This allows for enumerating the serivces in the cluster
and executing commands on remote machines. This initial cut is built on top of the
CM service to help with starting/stopping services. The long term goal is to let this run
on both a CM cluster and non-CM cluster as well as locally.

The other part of the failure injection change is failure_inctor module that uses the
Impala service abstraction to select and inject failures into random impala services.

This failure testing framework hasn't been completely validated because the product code
is not yet ready, but it is important to get this checked in so all new changes to
run-workload are based off this refactor.

Change-Id: I73bf44f0ac881ec17bea7cb05d850b45e2ea5be5

.gitignore

@@ -1,4 +1,5 @@
 *~
+*.pyc
 .*.swp
 derby.log
 thirdparty