Clarify ClientOnly documentation

The option is unneeded, not meaningless, so explain what it does.

Patch from Matt Pagan; fixes 9059.

changes/bug9059

+  o Documentation:
+    - Provide a more accurate description of the ClientOnly config
+      option on the man page. Resolves bug 9059.

doc/tor.1.txt

@@ -702,12 +702,13 @@ The following options are useful only for clients (that is, if
     number like 60. (Default: 0)
 
 [[ClientOnly]] **ClientOnly** **0**|**1**::
-    If set to 1, Tor will under no circumstances run as a relay or serve
-    directory requests. This config option is mostly meaningless: we
-    added it back when we were considering having Tor clients auto-promote
-    themselves to being relays if they were stable and fast enough. The
-    current behavior is simply that Tor is a client unless ORPort or
-    DirPort are configured. (Default: 0)
+    If set to 1, Tor will not run as a relay or serve
+    directory requests, even if the ORPort, ExtORPort, or DirPort options are
+    set. (This config option is
+    mostly unnecessary: we added it back when we were considering having
+    Tor clients auto-promote themselves to being relays if they were stable
+    and fast enough. The current behavior is simply that Tor is a client
+    unless ORPort, ExtORPort, or DirPort are configured.) (Default: 0)
 
 [[ExcludeNodes]] **ExcludeNodes** __node__,__node__,__...__::
     A list of identity fingerprints, nicknames, country codes and address