LU-10360 mgc: Use IR for client->MDS/OST connections

LU-10360 mgc: Use IR for client->MDS/OST connections

When a target registers with the MGS, the MGS sends an IR log
to the client to speed up recovery.

The IR log contains the updated NID information on the target
which just registered.

This patch allows clients to update their imports with the latest
NIDs for the targets reported in the IR log. It also allows clients
to create new connections for targets which were not added via
the config log.

For example if a target reboots and comes up with a new NID, then
the client can continue using it.

This functionality is disabled by default and can be enabled by
setting a new file system specific module parameter, dynamic_nids.

    lctl set_param mgc.*.dynamic_nids=1

This parameters will need to be set on the clients and the MGS

Signed-off-by: Amir Shehata <ashehata@whamcloud.com>
Change-Id: I9e85438c39a46d4950ac50309c1bbae2a96d7d5d
Reviewed-on: https://review.whamcloud.com/39613
Tested-by: jenkins <devops@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Mike Pershin <mpershin@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>