cfg: Improve nodestatusget versioning

Patch tries to make nodestatusget really extendable. Following changes
are implemented:

• corosync_cfg_node_status_version_t is added with (for now) single value CFG_NODE_STATUS_V1
• corosync_knet_node_status renamed to corosync_cfg_node_status_v1 (it isn't really knet because it works as well for udp(u()
• struct res_lib_cfg_nodestatusget_version is added which holds only ipc result header and version on same position as for corosync_cfg_node_status_v1
• corosync_cfg_node_status_get requires version and pointer to one of corosync_cfg_node_status_v structures
• request is handled in case switches to make adding new version easier

Also fix following bugs:

• totempg_nodestatus_get error was retyped to cs_error_t without any meaning.
• header.error was not checked at all in the library

Signed-off-by: Jan Friesse <jfriesse@redhat.com>
Reviewed-by: Christine Caulfield <ccaulfie@redhat.com>