[DOC] add missing parameters in SparkContext.scala for scala doc

[liyezhang556520]

No description provided.

[srowen]

I think that's OK, but if you're going to add some params, it would be better to put effort into fully adding missing params for a whole file or package.

[SparkQA]

Test build #41515 timed out for PR 8412 at commit 58e9d2e after a configured wait of 175m.

[liyezhang556520]

@srowen , I added the missing params for APIs that intending to adding params in the whole file. I'm wondering whether those missing @param are on purpose or not. Since in current spark code, there are many places missing @param and @return, if we want to make the doc better, I think someone need to open a JIRA to solve it.
And I submit this PR because SparkContext.scala is a very import file in spark core, and It's constructor APIs should be with complete scala docs.

[srowen]

No problem, I'll merge it. I don't think these were omitted on purpose. You might look over this one file and see if anything else needs a touch up.

[SparkQA]

Test build #1689 has finished for PR 8412 at commit 58e9d2e.

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

[SparkQA]

Test build #41530 timed out for PR 8412 at commit 8b41ddf after a configured wait of 175m.