Job's priority would be reset if it could not be immediately scheduled
AND if the best-fit node selection picked a DOWN node.

client and server are both reusing ports that match a defunct socket
connection in TIME_WAIT state. On this failure, we select a new random
port number and try again to connect.
(gnats:253)

from 2 to 5 seconds for slow tdev.

  - changed defs of HAVE_LIBELAN3 to HAVE_ELAN

   Elan3 and Elan4. Also allow old Elan3 module to work exactly
   the same as before.

   libelanctrl or libelan3

Send multiple SIGALRMs if needed and deal with possible abort of
a thread.