[SPARK-1395] Allow "local:" URIs to work on Yarn.

Don't distribute resources that have the "local" scheme
in their URIs.

Also fix an issue where the classpath for custom log4j
config files was incorrectly being set to include the
file's path (instead of its parent), and propagate the
user log4j configuration to the AM / workers. This has
the side effect of eliminating the "SPARK_YARN_LOG4J_CONF"
environment variable, which used to be used by the ExecutorRunner
class, in favor of the "SPARK_LOG4J_CONF" variable used
by the Yarn client class.