[SPARK-7341] [STREAMING] [TESTS] Fix the flaky test: org.apache.spark.stre...

...aming.InputStreamsSuite.socket input stream

Remove non-deterministic "Thread.sleep" and use deterministic strategies to fix the flaky failure: https://amplab.cs.berkeley.edu/jenkins/job/Spark-Master-Maven-pre-YARN/hadoop.version=1.0.4,label=centos/2127/testReport/junit/org.apache.spark.streaming/InputStreamsSuite/socket_input_stream/

Author: zsxwing <zsxwing@gmail.com>

Closes #5891 from zsxwing/SPARK-7341 and squashes the following commits:

611157a [zsxwing] Add wait methods to BatchCounter and use BatchCounter in InputStreamsSuite
014b58f [zsxwing] Use withXXX to clean up the resources
c9bf746 [zsxwing] Move 'waitForStart' into the 'start' method and fix the code style
9d0de6d [zsxwing] [SPARK-7341][Streaming][Tests] Fix the flaky test: org.apache.spark.streaming.InputStreamsSuite.socket input stream