CommandUtil: Fix NULL deref bug in CommonPreparePrologue
CommandUtil: Fix NULL deref bug in CommonPreparePrologue

Hiding use of variables in macros that take no parameters and have
variable names hard coded into them is generally a bad idea. This is an
example of why.

Signed-off-by: Philip Tricca <53a58e9d5471ed7186e9729c1e05c03a7332643a@twobit.us>

01org/TPM2.0-TSS,01org/tpm2-tss,tpm2-software/tpm2-tss,01org/TPM2.0-TSS,01org/TPM2.0-TSS,tpm2-software/tpm2-tss,01org/tpm2-tss,01org/TPM2.0-TSS,tpm2-software/tpm2-tss,01org/tpm2-tss