[SPARK-2703][Core]Make Tachyon related unit tests execute without deploying a Tachyon system locally.

[RongGu]

Make Tachyon related unit tests execute without deploying a Tachyon system locally.

[RongGu]

@haoyuan

[SparkQA]

Test build #22590 has started for PR 3030 at commit ad08827.

• This patch merges cleanly.

[SparkQA]

Test build #22590 has finished for PR 3030 at commit ad08827.

• This patch passes all tests.
• This patch merges cleanly.
• This patch adds no public classes.

[AmplabJenkins]

Test PASSed.
Refer to this link for build results (access rights to CI server needed):
https://amplab.cs.berkeley.edu/jenkins//job/SparkPullRequestBuilder/22590/
Test PASSed.

[haoyuan]

LGTM.

[pwendell]

Jenkins, retest this please. This looks good except I'm wondering - how long do these tests take? Is it more than 1 second?

[SparkQA]

Test build #23137 has started for PR 3030 at commit ad08827.

• This patch merges cleanly.

[SparkQA]

Test build #23137 has finished for PR 3030 at commit ad08827.

• This patch passes all tests.
• This patch merges cleanly.
• This patch adds no public classes.

[AmplabJenkins]

Test PASSed.
Refer to this link for build results (access rights to CI server needed):
https://amplab.cs.berkeley.edu/jenkins//job/SparkPullRequestBuilder/23137/
Test PASSed.

[pwendell]

This takes about 1.6 seconds. That's pretty long but I think it's fine for now (it would be nice if Tachyon could mock things to make this faster). I can merge this.

[JoshRosen]

It looks like this PR may have broken the Maven builds, but I'm not sure why:

https://amplab.cs.berkeley.edu/jenkins/job/Spark-Master-Maven-pre-YARN/955/
https://amplab.cs.berkeley.edu/jenkins/job/Spark-Master-Maven-with-YARN/882/