In later patches we'll need to abstract out more operations on a
per-service level, besides sv_shutdown and sv_function.

Declare a new svc_serv_ops struct to hold these operations, and move
sv_shutdown into this struct.
Signed-off-by: NShirley Ma <shirley.ma@oracle.com>
Acked-by: NJeff Layton <jlayton@primarydata.com>
Tested-by: NShirley Ma <shirley.ma@oracle.com>
Signed-off-by: NJ. Bruce Fields <bfields@redhat.com>