conpaas-core: fix clouds.base.Cloud._check_cloud_params
conpaas-core: fix clouds.base.Cloud._check_cloud_params

This patch improves _check_cloud_params by:

- calling get_cloud_type() to generate a proper error message where appropriate
- making it more explicit


git-svn-id: 3c739b8a310a10be68afd4fdd7f3d450bf1457ba@5118 ef35cc4a-2640-4bbf-98bc-65920db7d8ae

ema/conpaas,ema/conpaas,ema/conpaas,ema/conpaas,ema/conpaas