cpglockd: fix a startup race condition
    
    [root@clusternet-node1 shm]# cpglockd -f
    nodeid 1 already in group with PID 8126 8126
    Unable to join CPG group
    
    in some cases the cpg membership is updated between
    cpglockd joining and cpglockd requesting current membership,
    triggering the above error incorrectly.
    
    check if the pids are the same, we can be rather sure
    that it's us (given previous fix for startup pid/lock check)
    
    Signed-off-by: Fabio M. Di Nitto <fdinitto@redhat.com>
    Reviewed-by: Lon Hohberger <lhh@redhat.com>
    Reviewed-by: Ryan McCabe <rmccabe@redhat.com>