Tweak 'svnadmin info' output for packed FSFS filesystems.

* subversion/svnadmin/svnadmin.c
  (subcommand_info):
    Replace a tristate output field with two binary fields.  This adds
    information (there are four possible outputs, rather than three).  The
    old tristate output was misleading, since it could print "yes" and "no"
    like binary fields do.

New output:
    % svnadmin info 5 | me
    Filesystem Type: fsfs
    Filesystem Format: 6
    FSFS Sharded: yes
    FSFS Shard Size: 4
    FSFS Packed: yes
    FSFS Packable: no

git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1483879 13f79535-47bb-0310-9956-ffa450edef68