Revert "dns cache per interface iteration 2"

This reverts commit f1464ff956

Change-Id: I3496b9a8cb54614fe3eea016d1391c8a89f3db38

libc/docs/OVERVIEW.TXT

@@ -282,9 +282,16 @@ DNS resolver:
 
      - read /system/etc/resolv.conf instead of /etc/resolv.conf
 
-     - get the list of servers and the search domains for this process's
-       current interface from the dns cache.  This information is sent
-       from the framework via cache functions.
+     - read the list of servers from system properties. the code looks for
+       'net.dns1', 'net.dns2', etc.. Each property should contain the IP
+       address of a DNS server.
+
+       these properties are set/modified by other parts of the Android system
+       (e.g. the dhcpd daemon).
+
+       the implementation also supports per-process DNS server list, using the
+       properties 'net.dns1.<pid>', 'net.dns2.<pid>', etc... Where <pid> stands
+       for the numerical ID of the current process.
 
      - when performing a query, use a properly randomized Query ID (instead of
        a incremented one), for increased security.