Revert "Add third-party library for py-rrdtool, used by kwapi."

Kwapi uses now python-rrdtool instead of py-rrdtool, and python-rrdtool no longer requires librrd_dev library.

Change-Id: I8e00653974a1d336ea8039a29cd458b4d5eaace0
Reviewed-on: https://review.openstack.org/20474
Reviewed-by: Clark Boylan <clark.boylan@gmail.com>
Reviewed-by: Khai Do <do.khai@gmail.com>
Reviewed-by: James E. Blair <corvus@inaugust.com>
Approved: Jeremy Stanley <fungi@yuggoth.org>
Reviewed-by: Jeremy Stanley <fungi@yuggoth.org>
Tested-by: Jenkins