'extern' declarations should only appear in .h files.
All these names are declared in .h files as needed,
and these duplicate declarations in .c files can
be removed.

Test-Parameters: trivial

Change-Id: Ic563789f350fd21fd033f1d3c49cdac2125b86c5
Signed-off-by: NeilBrown <neilb@suse.com>
Reviewed-on: https://review.whamcloud.com/35294


Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Tested-by: Jenkins
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Arshad Hussain <arshad.super@gmail.com>
Reviewed-by: Petros Koutoupis <pkoutoupis@cray.com>