Don't run test1.83 if fewer than 3 nodes are available

testsuite/expect/test1.83

@@ -47,6 +47,12 @@ if {[test_front_end] != 0} {
 	exit 0
 }
 
+set available [available_nodes [default_partition]]
+if {$available < 3} {
+    send_user "\nWARNING: This test requires 3 nodes, but only $available available\n"
+    exit 0
+}
+
 #
 # Submit a 3 contiguous node job
 #