Initialize variable to prevent garbage values (RenderScriptRuntime)

The kernels_found variable is not initialized, so if it is not assigned true on line 823, then it will be a garbage value in the branch condition on line 828. This patch initializes the variable to false. 

Patch by neilparikh.

Reviewers: domipheus
Differential Revision: http://reviews.llvm.org/D11323

llvm-svn: 243104