journald: do not store the iovec entry for process commandline on stack
    
    This fixes a crash where we would read the commandline, whose length is under
    control of the sending program, and then crash when trying to create a stack
    allocation for it.
    
    CVE-2018-16864
    https://bugzilla.redhat.com/show_bug.cgi?id=1653855
    
    The message actually doesn't get written to disk, because
    journal_file_append_entry() returns -E2BIG.
    
    (cherry-picked from commit 084eeb865ca63887098e0945fb4e93c852b91b0f)
    
    Resolves: #1664976
    
    patch_name: 0070-journald-do-not-store-the-iovec-entry-for-process-co.patch
    present_in_specfile: true
    location_in_specfile: 70
    squash_commits: true