tests: destroy testprofile before creating one

tests: destroy testprofile before creating one

The testprofile erasure code profile is destroyed before creating a new
one so that it does not fail when another testprofile erasure code
profile already exists with different parameters.

This must be done when creating erasure coded pools with the C++
interface, in the same way it's done with the C interface.

http://tracker.ceph.com/issues/13664 Fixes: #13664

Signed-off-by: Loic Dachary <ldachary@redhat.com>