[SPARK-9570] [DOCS] Consistent recommendation for submitting spark apps to YARN, -master yarn --deploy-mode x vs -master yarn-x'.

[srowen]

Recommend --master yarn --deploy-mode {cluster,client} consistently in docs.
Follow-on to #8385
CC @nssalian

[tgravescs]

still using yarn-client here.

[SparkQA]

Test build #43196 has finished for PR 8968 at commit 47d9e8a.

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

[SparkQA]

Test build #43199 has finished for PR 8968 at commit e8db144.

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

[tgravescs]

@srowen , what happened here, why was this closed, it looks like it was committed but I don't see anyone +1. I was mostly good with it but it would have been nice to look at the final version.

[srowen]

Ah, I thought you had reviewed this and the previous iteration of this PR also? seemed pretty cut and dried to me at this stage. I don't know how long to wait for your explicit ack. In this case, being just docs, the downside of committing early is small -- you can always follow on with another commit if you really had something to add.