LU-11838 o2iblnd: get IP address more directly.

LU-11838 o2iblnd: get IP address more directly.

Use dev_get_by_name() and for_primary_ifa() to
get IP address for a named device.  This is more
direct.

Linux-commit: 10e138e41a4343fd1a88e4543990205d134e562a
Linux-commit: 9eb957b98aa6322abde33240bf50dd483c5d1190

This patch is back-ported from the following one:
Lustre-commit: 7a40cd2c83d174ae0bb7e22d62fad9fbd247a654
Lustre-change: https://review.whamcloud.com/33970

Change-Id: Ic4562c3948934bacb8613e9f6f57f609ecc04de7
Signed-off-by: NeilBrown <neilb@suse.com>
Signed-off-by: James Simmons <jsimmons@infradead.org>
Reviewed-by: Sonia Sharma <sharmaso@whamcloud.com>
Reviewed-by: Doug Oucharek <dougso@me.com>
Reviewed-on: https://review.whamcloud.com/35166
Tested-by: Jenkins
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: James Simmons <uja.ornl@yahoo.com>
Reviewed-by: Yang Sheng <ys@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>