LU-9859 lnet: simplifiy cfs_ip_addr_parse()

LU-9859 lnet: simplifiy cfs_ip_addr_parse()

cfs_ip_add_parse() is now always passed a string that it is safe to
modify.  So change the parsing to benefit from this and use standard
tools like strsep().

Note that the 'len' argument is now ignored.  It cannot be removed
without a larger change.

Test-Parameters: trivial testlist=sanity-lnet
Signed-off-by: Mr NeilBrown <neilb@suse.de>
Change-Id: Ice492edf109dca2e411132b891514f0caa535d8c
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/50842
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Frank Sehr <fsehr@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>
Reviewed-by: James Simmons <jsimmons@infradead.org>
Reviewed-by: Chris Horn <chris.horn@hpe.com>