remove heat-slow job and definition

The heat-slow job has been evaporating over time and no longer really
tests anything. The following ML thread is discussing it's future:

http://lists.openstack.org/pipermail/openstack-dev/2014-November/051506.html

Should the mailing list thread seem to come to consensus here, we
should approve this patch to match that policy.

Change-Id: I18c191e2c6fe4b4fff603c3fb0b29598b46403d5
Merge "remove heat-slow job and definition"