all I can say is that,I drove up to and on part of the Corniche ealier today, and yes I saw police and security men stopping people walking to the corniche. It seemed fine to just park up in a car.
Noticed most of the people they were stopping were groups of men.
Today for many was a well earned rest day, to spend time with family and friends.
I can only assume that 'someone' was going to travel on the corniche and 'they' did not want them to see the reality of Qatar - hard workers (I do have to admit it did seem like security were stopping only labour men in their casual clothes) who on a day off wish to do nothing than walk innocently on the corniche with friends.
Hey this is Qatar and 'they' can do what 'they' like when 'they' like!