BUG/MINOR: ssl/cli: fix "show ssl cert" not to mix cli+ssl contexts

BUG/MINOR: ssl/cli: fix "show ssl cert" not to mix cli+ssl contexts

The "show ssl cert" command mixes some generic pointers from the
"ctx.cli" struct with context-specific ones from "ctx.ssl" while both
are in a union. Amazingly, despite the use of both p0 and i0 to store
respectively a pointer to the current ckchs and a transaction id, there
was no overlap with the other pointers used during these operations,
but should these fields be reordered or slightly updated this will break.
Comments were added above the faulty functions to indicate which fields
they are using.

This needs to be backported to 2.5.