erasure-code: add various erasure-code workloads

The erasure-code directory is populated with files describing rados
workloads suitable to test the default erasure code plugins. They are
linked to the rados suite. The pre-existing rados workloads from the
rados suite are replaced with those. Two workloads only differed by the
fact that one of them had less operations than the other. The more
complete set of operations is kept and used for all workloads to
maximize coverage.

Signed-off-by: Loic Dachary <loic-201408@dachary.org>