LU-4423 lustre: don't declare extern variables in C files.

LU-4423 lustre: don't declare extern variables in C files.

A previous patch already removes some 'extern's.  This patch
removes the remainder from kernel code.

Signed-off-by: Mr NeilBrown <neilb@suse.de>
Change-Id: If78d96edd389c602ac8ee3321492db5fedda7c69
Reviewed-on: https://review.whamcloud.com/36650
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Ben Evans <bevans@cray.com>
Reviewed-by: James Simmons <jsimmons@infradead.org>
Reviewed-by: Petros Koutoupis <pkoutoupis@cray.com>
Reviewed-by: Shaun Tancheff <stancheff@cray.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>