[SPARK-1112, 2156] (1.0 edition) Use correct akka frame size and overhead amounts.

SPARK-1112: This is a more conservative version of #1132 that doesn't change
around the actor system initialization on the executor. Instead we just
directly read the current frame size limit from the ActorSystem.

SPARK-2156: This uses the same fixe as in #1132.

Author: Patrick Wendell <pwendell@gmail.com>

Closes #1172 from pwendell/akka-10-fix and squashes the following commits:

d56297e [Patrick Wendell] Set limit in LocalBackend to preserve test expectations
9f5ed19 [Patrick Wendell] [SPARK-1112, 2156] (1.0 edition) Use correct akka frame size and overhead amounts.