Land b1_4_smallfix onto b1_4 (20041125_1716)

Land b1_4_smallfix onto b1_4 (20041125_1716)
- don't keep a lock reference when lock is not granted (b=4238)
- unsafe list practices (rarely) led to infinite eviction loop (b=4908)
- add per-fs limit of Lustre pages in page cache, avoid OOM (b=4699)
- drop import inflight refcount on signal_completed_replay error (b=5255)
- unlock page after async write error during send (b=3677)
- service request history (b=4965)
- put {ll,lov,osc}_async_page structs in a single slab (b=4699)
- create an "evict_client" /proc entry on OSTs, like the MDS has
- handle missing objects in filter_preprw_read properly (b=5265)