LU-11893 lnet: consoldate secondary IP address handling

LU-11893 lnet: consoldate secondary IP address handling

The last piece of code with broken secondary IP address
support is lnet_parse_ip2nets(). We could fix it like
o2iblnd or socklnd was done but since the LND drivers
resolved those issues instead we can move the handling
out of the LND drivers into one place in the LNet core.
To do this we introduce struct lnet_inetdev which is
a collection of data that the current LNet layer requires.
The new function lnet_inet_enumerate() is used to collect
this information.

This patch is back-ported from the following one:
Lustre-commit: d6d0194c1969db05a6a60718679750ecfd75739b
Lustre-change: https://review.whamcloud.com/34993

Change-Id: I0c532caa3cf6b2178eb1ab65e55e5883d408a185
Signed-off-by: James Simmons <uja.ornl@yahoo.com>
Signed-off-by: James Simmons <jsimmons@infradead.org>
Reviewed-on: https://review.whamcloud.com/35442
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Chris Horn <hornc@cray.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>