When Robyn Black rushed her beloved corgi Winston to a veterinary hospital in Sacramento, she told the staff to do whatever it took to heal her pup as an autoimmune disease threatened his life. Winston needed several blood transfusions, but after two days of treatment, the veterinary hospital ran out of the canine lifeline. Pet hospitals often are short on dog blood amid a national shortage that lawmakers say is further exacerbated in California by the state’s restrictive laws that require veterinarians to buy dog blood solely from two blood…