Add option to log UTC timestamps
    
    To make it easier to debug cluster issues, management system may like to
    use UTC timestamps on all machines in the cluster.  This patch adds a
    logfile_use_utc option to allow a management system to configure sanlock
    for its needs. The default is 0, keeping old behaviour expected by
    existing users.
    
    Signed-off-by: Nir Soffer <nsoffer@redhat.com>