[linux-cifs-client] fix for readpages leak (various symptoms reported)

[Steve French]

Found the extra reference to read ahead pages in cifs_readpages that
caused memory leak (extra call to page_cache_get).

http://cvs.samba.org/samba/ftp/cifs-cvs/cifs-1.0.7a-2.6.tar.gz

This fixes the problem but caching is not working as expected so
performance is a bit slower when I just ran iozone.   I will look at
this, but other tests I ran are doing ok.  

Minor issues - a timing problem with reference counts on files
resurfaced on one of my test machines with hardlinks - this is an old
issue that is hard to solve in the protocol. The reference count will be
correct within a few seconds but cthon checks it immediately.  I will
see if I can find a workaround.

Have not debugged the permissions problem reported on the list yesterday
(will look at that soon).