Remove CPURuntimeContext mkldnn primitives and workspaces assignments for CODEGEN. CODEGEN uses CPURuntimeContextCG mkldnn primitives and workspaces.
Remove CPURuntimeContext mkldnn primitives and workspaces assignments for CODEGEN.
CODEGEN uses CPURuntimeContextCG mkldnn primitives and workspaces.

NervanaSystems/ngraph,NervanaSystems/ngraph,NervanaSystems/ngraph,NervanaSystems/ngraph