Both cause the 'entries' count in the export cache to be non-zero at module
removal time, so unregistering that cache fails and results in an oops.

1/ exp_pseudoroot (used for NFSv4 only) leaks a reference to an export
   entry.
2/ sunrpc_cache_update doesn't increment the entries count when it adds
   an entry.

Thanks to "david m.  richter" <richterd@citi.umich.edu> for triggering the
problem and finding one of the bugs.

Cc: "david m. richter" <richterd@citi.umich.edu>
Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>