Fix caching in the Spark streaming, doing the cache update in the str…

[jbonofre]

…eaming context

Be sure to do all of the following to help us incorporate your contribution
quickly and easily:

• Make sure the PR title is formatted like:
  [BEAM-<Jira issue #>] Description of pull request
• Make sure tests pass via mvn clean verify. (Even better, enable
  Travis-CI on your fork and ensure the whole test matrix passes).
• Replace <Jira issue #> in the title with the actual Jira issue
  number, if there is one.
• If this contribution is large, please file an Apache
  Individual Contributor License Agreement.

---

[jbonofre]

R: @amitsela
R: @aviemzur

[jbonofre]

Run Spark RunnableOnService

[asfbot]

Refer to this link for build results (access rights to CI server needed):
https://builds.apache.org/job/beam_PostCommit_Java_RunnableOnService_Spark/1357/
--none--

[coveralls]

Coverage decreased (-0.006%) to 70.098% when pulling d25d73b on jbonofre:FIX_CACHING_SPARK_STREAMING into 14aba81 on apache:master.

[coveralls]

Coverage decreased (-0.003%) to 70.102% when pulling d25d73b on jbonofre:FIX_CACHING_SPARK_STREAMING into 14aba81 on apache:master.

[asfbot]

Refer to this link for build results (access rights to CI server needed):
https://builds.apache.org/job/beam_PostCommit_Java_RunnableOnService_Spark/1358/
--none--

[asfbot]

Refer to this link for build results (access rights to CI server needed):
https://builds.apache.org/job/beam_PreCommit_Java_MavenInstall/8764/
--none--

[asfbot]

Refer to this link for build results (access rights to CI server needed):
https://builds.apache.org/job/beam_PreCommit_Java_MavenInstall/8765/
--none--

[jbonofre]

Tests passed (including ROS).

[aviemzur]

LGTM!

[amitsela]

I'll merge since this became a blocker for other PRs.