cleanup the ceph-erasure-code-corpus directory

In the same way it is done for the ceph-object-corpus directory.

http://tracker.ceph.com/issues/9420 Refs: #9420

Signed-off-by: Loic Dachary <loic-201408@dachary.org>
Merge pull request #18 from dachary/wip-erasure-code-corpus

cleanup the ceph-erasure-code-corpus directory