staging/lustre/llite: drop_caches hangs in cl_inode_fini()

This patch releases cl_pages on error in ll_write_begin()
to avoid memory and object reference leaks. Also, it
reuses per-cpu lu_env in ll_invalidatepage() in the same
way as done in ll_releasepage().

Signed-off-by: Andrew Perepechko <andrew.perepechko@seagate.com>
Seagate-bug-id: MRP-3504
Reviewed-on: http://review.whamcloud.com/22745
Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-8509


Reviewed-by: Jinshan Xiong <jinshan.xiong@intel.com>
Reviewed-by: Bobi Jam <bobijam@hotmail.com>
Signed-off-by: Oleg Drokin <green@linuxhacker.ru>
Reviewed-by: James Simmons <jsimmons@infradead.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>