support var_step when container concurrence

[tsjsdbd]

it's already support var_iter when job concurrence.

var1: [A,B,C]
var2:[1,2,3]
it get : A1, A2, A3, B1, B2, B3, C1, C2, C3

but, when container job concurrence，it need all $vars iterater both add index like:

var1: [A,B,C]
var2:[1,2,3]
it get : A1, B2, C3