http: avoid dns reverse lookup on HttpProtocolInfo#toString()

Motivation:

 - billing performance depends on DNS server
 - not secure.

Modification:
 use Inetaddress#getHostAddress() instead of Inetaddress#getHostName()

Result:
no extra dns lookups.
billing file will contain ip address

Acked-by:
Target: master, 2.15, 2.14, 2.13
Require-book: no
Require-notes: yes

modules/dcache-vehicles/src/main/java/diskCacheV111/vehicles/HttpProtocolInfo.java

@@ -146,7 +146,7 @@ public String toString()
   {
     StringBuilder sb = new StringBuilder() ;
     sb.append(getVersionString()) ;
-    sb.append(':').append(_clientSocketAddress.getAddress().getHostName());
+    sb.append(':').append(_clientSocketAddress.getAddress().getHostAddress());
     sb.append(':').append(_clientSocketAddress.getPort()) ;
     sb.append(':').append(httpDoorCellName);
     sb.append(':').append(httpDoorDomainName);