[SPARK-4933][CORE] eventlog file not found

[liyezhang556520]

enent log file not found exception will be thrown after making eventLog into a single file. And web ui will show "No event logs found for application xxx in xxx". Main cause is the wrong argument when getting log file.

[SparkQA]

Test build #24734 has started for PR 3777 at commit 5b5fb3f.

• This patch merges cleanly.

[SparkQA]

Test build #24734 has finished for PR 3777 at commit 5b5fb3f.

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

[AmplabJenkins]

Test PASSed.
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https://amplab.cs.berkeley.edu/jenkins//job/SparkPullRequestBuilder/24734/
Test PASSed.

[JoshRosen]

/cc @andrewor14 @vanzin

[vanzin]

#3755?

[JoshRosen]

Ah, gotcha; looks like a duplicate. I'll mark this as a duplicate on JIRA and take a review pass through that other PR (if it's good to go, I'll merge it). Thanks for the pointer!