[SPARK-11129][MESOS] Link Spark WebUI from Mesos WebUI

[philipphoffmann]

Mesos has a feature for linking to frameworks running on top of Mesos
from the Mesos WebUI. This commit enables Spark to make use of this
feature so one can directly visit the running Spark WebUIs from the
Mesos WebUI.

[JoshRosen]

@tnachen

[andrewor14]

ok to test

[SparkQA]

Test build #43811 has finished for PR 9135 at commit 63ed22e.

• This patch fails Scala style tests.
• This patch merges cleanly.
• This patch adds no public classes.

[philipphoffmann]

fixed the style issue

[SparkQA]

Test build #43837 has finished for PR 9135 at commit 22f3c6d.

• This patch fails Spark unit tests.
• This patch merges cleanly.
• This patch adds no public classes.

[philipphoffmann]

Hey @andrewor14 I'm pretty sure the failing test is unrelated (seems to be a timing issue). Is there a way to just trigger the build again?

[tnachen]

LGTM

[andrewor14]

yup, it's likely not your fault. retest this please

[SparkQA]

Test build #43842 has finished for PR 9135 at commit 22f3c6d.

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

[JoshRosen]

LGTM as well, so I'm going to merge this into master.