Check VIM juju paas config

It must contain :

- paas_provider
- ca_cert_content
- cloud
- cloud_credentials

Change-Id: I8ce9918f81afd120c7a3d4e1e05fe27fac3508ad
Signed-off-by: Patricia Reinoso <patricia.reinoso@canonical.com>
Signed-off-by: Mark Beierl <mark.beierl@canonical.com>