Fix error in v3 credentials create/update

The v3 credentials passes data associated with the credential in
a "data" key, but the underlying API expects "blob", which is also
what is documented in the API spec.

Currently any attempt to create a credential with a type of 'ec2'
will fail with 'Invalid blob in credential' So s/data/blob to fix.

Change-Id: I0858e8c39653477eb554ee9d15fb4f2dde2b195c
Closes-Bug: #1259461
v3 test utils, don't modify input parameter

As mentioned in https://review.openstack.org/#/c/61046/ for
test_update, we should not modify the input req_ref in test_create
instead we should make a copy

Change-Id: I649433596a3ebbf2133eb724f09eb4bd470b7cdd
Merge "Fix error in v3 credentials create/update"
Merge "v3 test utils, don't modify input parameter"