logsys: Remove config mutex

The logsys component is internal to Corosync and used only by the main
thread. Since Corosync is single-threaded, this mutex is needless
and is removed to avoid unnecessary performance overhead.

Special thanks to Christine Caulfield <ccaulfie@redhat.com> for opening
this idea.

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