Correctly set cinder storage_protocol and vendor_name

We take the first non-LVM backend and do the right thing.

Fix failures in
tempest.api.volume.admin.test_volume_types.VolumeTypesTest.test_create_get_delete_volume_with_volume_type_and_extra_specs
when only these backends are used.
Merge pull request #105 from vuntz/cinder-vendor-protocol

Correctly set cinder storage_protocol and vendor_name