This commit removes the option to change the netty system properties to
reenable the direct buffer pooling. It also removes the need for us to
disable the buffer pooling in the system properties file. Instead, we
programmatically craete an allocator that is used by our networking
layer.
This commit does introduce an Elasticsearch property which allows the
user to fallback on the netty default allocator. If they choose this
option, they can configure the default allocator how they wish using the
standard netty properties.
547e399dbf