LU-6142 lustre: mark strings in char arrays as const

LU-6142 lustre: mark strings in char arrays as const

Most array of strings are marked 'const', but the strings within the
arrays often aren't.
This patch mark all strings in const arrays of strings as const.
This allows them to be placed in read-only memory.

Test-Parameters: trivial
Signed-off-by: Mr NeilBrown <neilb@suse.de>
Change-Id: I93b627e646e446fc48d9b76f1d5e9da9d12b4395
Reviewed-on: https://review.whamcloud.com/39742
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: James Simmons <jsimmons@infradead.org>
Reviewed-by: Shaun Tancheff <shaun.tancheff@hpe.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>