Fix and PTL testcase for missing node attr

Incorporated the changes requested in PR

src/server/node_manager.c

@@ -8594,6 +8594,9 @@ set_last_used_time_node(void *pobj, int type)
 				snprintf(str_val, sizeof(str_val), "%d", time_int_val);
 				set_attr_svr(&(pnode->nd_attr[(int)ND_ATR_last_used_time]),
 						&node_attr_def[(int) ND_ATR_last_used_time], str_val);
+				pnode->nd_modified = NODE_UPDATE_OTHERS;
+				if(svr_chngNodesfile == 0)
+					svr_chngNodesfile = 1; /*make sure nodes are saved to the database during shutdown*/
 			}
 		}
 		last_pn = pn;

test/tests/functional/pbs_pbsnodes.py

@@ -89,3 +89,21 @@ def test_pbsnodes_aS(self):
             self.assertIn(
                 hdr, out2['out'][0],
                 "header %s not found in output" % hdr)
+
+    def test_pbsnodes_av(self):
+        """
+        This verifies the values of last_used_time in 'pbsnodes -av'
+        result before and after server shutdown, once a job submitted.
+        """
+        j = Job(TEST_USER)
+        j.set_sleep_time(1)
+        jid = self.server.submit(j)
+        self.server.accounting_match("E;%s;" % jid)
+        prev = self.server.status(NODE, 'last_used_time')[0]['last_used_time']
+        self.logger.info("Restarting server")
+        self.server.restart()
+        self.assertTrue(self.server.isUp(), 'Failed to restart Server Daemon')
+        now = self.server.status(NODE, 'last_used_time')[0]['last_used_time']
+        self.logger.info("Before: " + prev + ". After: " + now + ".")
+        self.assertEquals(prev.strip(), now.strip(),
+                          'Last used time mismatch after server restart')