Fixed ScriptGroup for outputs to globals

b/21187932

Dependency from one kernel to another kernel -- where one reads the
other's output to a global allocation -- was not handled correctly.
This CL fixed that. Needed to make a new CTS test pass.

Change-Id: I500f9cac9d89bcaec7c186e942ba4a7d413daadb
(cherry picked from commit 85858718c0fc8f4f17ee18e5d62ec0614a8bc780)