EX-8270 ptlrpc: reduce usage of pool_index

EX-8270 ptlrpc: reduce usage of pool_index

The pool index is used over and over a lot of places where
we should just use it once.

Note the printing functions are deliberately not combined
to maximum length lines for ease of reading.

Test-Parameters: trivial
Signed-off-by: Patrick Farrell <pfarrell@whamcloud.com>
Change-Id: I7efbf491cf28f6fd16d06f5bbc42d714c908f34c
Reviewed-on: https://review.whamcloud.com/c/ex/lustre-release/+/52436
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>