[SPARK-9212][CORE] upgrade Netty version to 4.0.29.Final

[liyezhang556520]

related JIRA: SPARK-9212 and SPARK-8101

[srowen]

I think this is fine based on previous discussion. Is there any additional change to make here? you say it makes it possible to avoid some memory-related hack? or is that inside netty?

[liyezhang556520]

Maybe I made a misleading expression with "hack", I meant I didn't find a way to go into netty to get the memory usage for old versions since they didn't provide any public APIs.
And I think there is no additional change to make here.

[SparkQA]

Test build #37922 has finished for PR 7562 at commit 1917729.

• This patch passes all tests.
• This patch merges cleanly.
• This patch adds the following public classes (experimental):
  • trait ExpectsInputTypes extends Expression
  • trait ImplicitCastInputTypes extends ExpectsInputTypes
  • trait Unevaluable extends Expression
  • trait Nondeterministic extends Expression
  • trait CodegenFallback extends Expression
  • case class Hex(child: Expression) extends UnaryExpression with ImplicitCastInputTypes
  • case class Unhex(child: Expression) extends UnaryExpression with ImplicitCastInputTypes