LU-9855 lustre: rename obd_device variables to obd

Most variables of type 'struct obd_device *' are named 'obd' -
655 of them.

81 are named 'dev'
29 are named 'obddev'

The remainder (< 100) have various names specific to the used (e.g
disk_obd, src, tgt etc), none used more than 11 times (mgc).

As 'obd', 'dev', and 'obddev' are all simple generic names, it would
be nice to be consistent and only use one of these.

This patch changes all 'dev' and 'obddev' variables to 'obd'.

Also change some "sprintf" to "scnprintf .. PAGE_SIZE" to avoid
warnings.

Test-Parameters: trivial
Signed-off-by: Mr NeilBrown <neilb@suse.de>
Change-Id: I640c4f121d7db6aec1fef848a84463d46f68f262
Reviewed-on: https://review.whamcloud.com/36969
Tested-by: Maloo <maloo@whamcloud.com>
Tested-by: jenkins <devops@whamcloud.com>
Reviewed-by: James Simmons <jsimmons@infradead.org>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>