Mention the min duration for nodesuspend explicitly

Although currently this is documented in virsh man page
and virsh help, the expicit mention in the error message
is helful for tools using the API directly.
Signed-off-by: NNitesh Konkar <nitkon12@linux.vnet.ibm.com>

src/util/virnodesuspend.c

@@ -76,7 +76,9 @@ static int virNodeSuspendSetNodeWakeup(unsigned long long alarmTime)
     int ret = -1;
 
     if (alarmTime < MIN_TIME_REQ_FOR_SUSPEND) {
-        virReportError(VIR_ERR_INVALID_ARG, "%s", _("Suspend duration is too short"));
+        virReportError(VIR_ERR_INVALID_ARG,
+                       _("Suspend duration is too short, must be at least %u seconds"),
+                       MIN_TIME_REQ_FOR_SUSPEND);
         return -1;
     }