Fixes #550 - Note that encrypt is the default option

There are two options to hprop.  It's important to note that the default
behavior is to transmit the database with encrypted keys.

(cherry picked from commit 68f74fb)

kdc/hprop.8

@@ -115,7 +115,8 @@ The encryption keys in the database can either be in clear, or
 encrypted with a master key. This option transmits the database with
 unencrypted keys.
 .It Fl E , Fl Fl encrypt
-This option transmits the database with encrypted keys.
+This option transmits the database with encrypted keys. This is the
+default if no option is supplied.
 .It Fl n , Fl Fl stdout
 Dump the database on stdout, in a format that can be fed to hpropd.
 .El