By Hyunjoo Jin and Nivedita Balu SAN FRANCISCO (Reuters) – Tesla buyers who waited months for their new car have had an unusual choice for much of the past two years: keep the new electric vehicle, or sell it at a profit to someone with less patience. But the days of the Tesla flip are numbered – a potential threat to new car prices that are already getting cut. Prices of used Teslas are falling faster than those of other carmakers and the clean-energy status symbols are languishing in dealer lots longer, industry data provided to Reuters showed. The average price for a used Tesla in November …