Fix CounterController Metric value type & add tests

[ilayaperumalg]

• The metric value type used in the CounterController is set to use Long instead of Double
  • Add CounterControllerTests

Resolves #526
Resolves #460

[markpollack]

The RedisMetricRepository in boot actually is returning a Metric, see https://github.com/spring-projects/spring-boot/blob/master/spring-boot-actuator/src/main/java/org/springframework/boot/actuate/metrics/repository/redis/RedisMetricRepository.java#L182

[ilayaperumalg]

It is weird that the DefaultCounterService uses Double and will have problem when using this as a CounterService. Since data flow explicitly uses RedisCounterRepository, I have updated this PR to use Double as the metric value type and updated the tests to use RedisCounterRepository.

[markpollack]

Getting a test failure on testList

java.lang.AssertionError: JSON path "$.page.totalElements"
Expected: is <2>
     but: was <3>
    at org.hamcrest.MatcherAssert.assertThat(MatcherAssert.java:20)
    at org.springframework.test.util.JsonPathExpectationsHelper.assertValue(JsonPathExpectationsHelper.java:103)
    at org.springframework.test.web.servlet.result.JsonPathResultMatchers$1.match(JsonPathResultMatchers.java:65)
    at org.springframework.test.web.servlet.MockMvc$1.andExpect(MockMvc.java:171)
    at org.springframework.cloud.dataflow.server.controller.CounterControllerTests.testList(CounterControllerTests.java:94)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)
    at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
    at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
    at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
    at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:26)

[markpollack]

I cleaned redis and it worked, not sure the root cause as I didn't look at my keys/contents before flushing....