Don't default to master host-uuid if sr-create shared=false

sr-create had been defaulting the host-uuid to master if it wasn't
specified. This would cause problems when creating a local SR without
specifying the host-uuid. We now raise a CLI exception if we create
non-shared SR without specifying the host-uuid.

CA-98185

Signed-off-by: Mike McClurg <mike.mcclurg@citrix.com>