Add a Wait(int sec) method to XrdSysSemaphore, replace all usage of XrdSysSemWait
with XrdSysSemaphore, and remove XrdSysSemWait. The motivation is that XrdSysSemaphore
guards against spurious condition variable wakeup and XrdSysSemWait does not. Also
remove the possibility of an infinite loop in the Wait(int)
and WaitMS(int) methods of XrdSysCondVar.