Review 25377

C. Thomas Tyler
Removed journalPrefix as command line paramter during journal
rotation, deferring to db.config values.

Removed explicit specification of journalPrefix as a command line
argument to 'p4 admin journal' and 'p4d -jj' commands.  Specifying
the prefix is redundant as journalPrefix values are defined for the
master server and any/all replicas/edge servers in db.config, and
db.config is the One Source of Truth for journalPrefix.

The SDP defines best practice values for journalPrefix, with
elements of this in (setting configurables for replicas)
and (preparing directories during initial installation).

Note that verifies that journalPrefix values are
correct as per SDP standards.

Also cleaned up comments.

#review @mshields
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