task/: add ec_pool and append to rados.py

Signed-off-by: Samuel Just <sam.just@inktank.com>
radosbench: simplify pool creation and add ec_pool support

Signed-off-by: Samuel Just <sam.just@inktank.com>
task/peering_speed_test.py: add test which summarizes pg peering speed

Running this regularly may warn us about slow peering.

Signed-off-by: Samuel Just <sam.just@inktank.com>
working