core: Determine file storage type by user.

Importing a Storage Domain should be determined by the user instead it
will be determined from the meta data.
Alao removing unrequired related CDA message, and a test which is not
relevant anymore.

Change-Id: I1251c51b06bcd5f17633a4ad3de2496d5cb77683
Bug-Url: https://bugzilla.redhat.com/1157240
Signed-off-by: Maor Lipchuk <mlipchuk@redhat.com>