WASHINGTON, May 4 (Reuters) - Fears that U.S. cities would be emptied by the coronavirus pandemic are giving way to potential signs of revival, according to a series of analyses that suggest any dislocation from the last year will prove temporary. Some data suggest a return is already underway. Cellphone tracking firm Unacast had earlier noted that phone users were shifting their overnight locations out of New York, but now sees them coming back. "New York is growing again," with the city adding a net 1,900 people in the first two months of 2021 versus a loss of 7,100 in...