glGetActiveUniformBlockiv was using the current program
instead of using the program passed as an argument to
the function, causing it to misbehave.

Change-Id: I69b640b20793bd8e7e0c4142a1ff74d0ea796747
Reviewed-on: https://swiftshader-review.googlesource.com/3583Reviewed-by: Nicolas Capens <capn@google.com>
Tested-by: Alexis Hétu <sugoi@google.com>