int cpg_leave(cpg_handle_t handle, struct cpg_name *group);
function is used to leave a group. Once a group has been left the process will
no longer receive messages or notifications about events in that group.
Note that a process is only deemed to have left the group once it has been
notified (by its confchg callback) that is has left.
So expect to receive at least one confchg callback after calling this function.
is used to specify the group to leave. It is currently ignored as only one group
can be joined per handle. It is included here for to allow for future development.
This call returns the CPG_OK value if successful, otherwise an error is returned.