CLOUDSTACK-6924. To attach a volume if a volume needs to be moved to another storage
pool, the source and destination pools cannot be local and cluster/zone and vice versa.
Cloudstack detects it and throws a exception. However, the end user only sees an
unexpected exception and not the reason for failure. Fixed it by making sure the
reason for the failure is correctly captured and shown to the end user.
While adding secondary storage / is not added to secondary storage cifs url.
This causes it to fail if that path doesn't begin with '/'. It works fine
while adding primary storage. Added a check to add '/' in begining if needed.