Set home-cluster while creating an array

Set home-cluster while creating an array

The home-cluster is stored in the bitmap super block of the
array. The device can be assembled on a cluster with the
cluster name same as the one recorded in the bitmap.

If home-cluster is not specified, this is auto-detected using
dlopen corosync cmap library.

neilb: allow code to compile when corosync-devel is not installed.

Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.com>
Signed-off-by: Guoqing Jiang <gqjiang@suse.com>
Signed-off-by: NeilBrown <neilb@suse.de>