LU-12410 lnet: Convert lnetctl peer add and del

LU-12410 lnet: Convert lnetctl peer add and del

Convert the lnetctl peer add and del commands to utilize the new
capabilities provided by the nidstrings library.

Test-Parameters: trivial
Test-Parameters: testlist=sanity-lnet
Signed-off-by: Chris Horn <hornc@cray.com>
Change-Id: I50693a2af6fef2e1ef3b34fd02c7423625cb7665
Reviewed-on: https://review.whamcloud.com/35305
Reviewed-by: Shaun Tancheff <stancheff@cray.com>
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Petros Koutoupis <pkoutoupis@cray.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>