[SPARK-22660][BUILD] Use position() and limit() to fix ambiguity issue in scala-2.12

[kellyzly]

What changes were proposed in this pull request?

Missing some changes about limit in TaskSetManager.scala

How was this patch tested?

running tests

Please review http://spark.apache.org/contributing.html before opening a pull request.

[SparkQA]

Test build #4010 has finished for PR 19976 at commit bcc4c1a.

• This patch fails PySpark pip packaging tests.
• This patch merges cleanly.
• This patch adds no public classes.

[SparkQA]

Test build #4011 has finished for PR 19976 at commit bcc4c1a.

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

[srowen]

Merged to master