group (distinct x) all; gives a nonsense bag name in the resulting schema

[Jonathan Coveney]

On pig9, if you do the following:

a = load 'thing' as (x:int); b = group (distinct a) by $0; describe b;

the schema is:

b: {group: int,1-631: {(x: int)}}

Every time you run the above, the range will change. This is also an issue
in trunk. I can open a ticket if there is nothing currently?