Refactor agent-integration tests
Refactor agent-integration tests

Extract restarting redis method
Simplify checkRedisStopped method
Replace Omega with Expect

[#162387263]

Signed-off-by: James Norman <ee17c86653c1b33db95db3d5b42fdcc2c8764b22@pivotal.io>

pivotal-cf/cf-redis-broker,pivotal-cf/cf-redis-broker