Searching PsActiveProcessList for sysproc.

Addressing an issue during init of a live VM where
PsActiveProcessHead can be resolved by kdbg but
PsInitialSystemProcess can't, where the EPROCESS at
PsActiveProcessHead is not the system process.

Calling eprocess_search implicitly uses the "not real"
value for kpgd.  The previous implementations call to
translate_kvp2 does as well, this just does it a lot
more.